Methods of and sludge collector with adjacent opposed oppositely-moving blades for moving sludge in a basin

ABSTRACT

Apparatus and methods provide individual blades driven by drives configured to reduce a tendency of sludge to be moved in an undesired return direction. Drive configurations apply “pull” and “pull” forces that only pull on tensile structures, avoiding a need in actual commercial practice for use of extra structural drive members having high resistance to both tension and compressive forces exerted parallel to a sludge movement direction. Each of two separate tensile structures carries one blade, or a separate set of blades, with blade(s) of one structure adjacent to, and alternating with, blade(s) of the other structure. Embodiments move sludge from a corner of a basin and across a floor of the basin. The reduced tendency of sludge movement in the return direction results from moving one tensile structure and blade(s) in the sludge movement direction as the other tensile structure and adjacent opposed blade(s) move in the return direction.

BACKGROUND

1. Field

The present invention relates generally to removing materials fromliquids, and more particularly to adjacent opposed, oppositely movingblades for, and methods of, moving sludge in a sludge collection basinfor removal of the sludge from the basin.

2. Description of the Related Art

In the past, containers (e.g., basins or tanks) have been provided tohouse apparatus in which materials are collected. The materials may haveany of a wide variety of compositions, and generally consist of piecesof the materials that move under the force of gravity to the bottom (orfloor) of the basin (“settleable-particles”). For example, in municipalwaste water systems, the materials may be formerly biologically-activewaste materials that are no longer biologically-active, and that are inthe form of the settleable-particles.

For ease of description, materials within the wide range of compositionsand that consist of the settleable-particles, are referred to as“particles”, and in the context of particles that have settled, ormoved, to the bottom of the basin, such materials are referred to as“sludge”.

The settleable-particles may be collected from liquids by plate or tubesettlers that promote settling of the settleable-particles to the bottomof the basin. In other cases, flocculators may be housed in suchcontainers. Settleable-particles often inadvertently move in theflocculators to the bottom of the basin. Because the flocculators aredesigned to circulate liquid and materials, rather than to promotesettling of the materials, the materials that inadvertently collect atthe bottom of the basin present a problem.

In the case of the settlers, for example, the sludge must be removedfrom the bottom to make room for more sludge collected from more liquidand materials that flow into the basin. In the past, sludge removalequipment has been mounted on or near the bottom for moving the sludgealong the bottom to sludge outlets that allow removal of the sludge fromthe basin. The moving has been done by scrapers that are mountedtogether for traverse together from one end of the basin to an oppositeend of the basin. On each traverse in one direction, each of thescrapers pushes sludge in the same direction to the outlet at one end.On each reverse traverse in the opposite direction, each of the scraperspushes sludge to the outlet at the other end. In this scraper system,the scrapers must be able to push the sludge in each of the directions,and move together in the respective direction to perform the pushing.

Others have attempted to use scrapers of a different design, in whichthe scrapers need only be able to push the sludge in one directionacross the bottom while moving together in the one direction to performthe pushing. In the use of these different scrapers, such as thosedescribed in U.S. Pat. No. 5,431,818 to K. D. Zickert issued Jul. 11,1995, the distance through which each of the scrapers is moved has beengreatly reduced, e.g., to about two feet. Problems are described in thatpatent in the use of a wedge-shaped scraper having a generallyright-triangular cross-section, such as the scrapers 30 shown in FIGS.1A and 1B. Many such scrapers 30 are attached to one net 32. The one net32 is moved in a “to” (forward, sludge-moving direction, arrow 34) andin a “fro” (return, or reverse direction, arrow 36) reversing traverse.In this manner, the one net 32 moves all of the scrapers 30 together inone time period (TP) through the two foot distance in one direction(e.g., the forward, “to”, direction 34, FIG. 1A). The one net 32 thenreverses, and moves all of the scrapers 30 together in a next TP throughthe same two foot distance in the opposite direction (arrows 36, FIG.1B).

In an effort to increase the efficiency of sludge movement in theforward direction 34, in U.S. Pat. No. 5,431,818 the cross-section ofthe scrapers 30 was modified, and all of the modified scrapers 40 (FIGS.1C and 1D) were moved together in the same “to” direction 34 andtogether in the “fro” direction 36 at controlled speeds in the same timeperiods. Unfortunately, that cross-section of the modified scrapers 40was made more complex by the selection of a curved configuration 41shown in FIGS. 1C and 1D. That configuration 41 was described as adownwardly facing bottom surface 42, a substantially oblique, convexsurface 44, and a substantially vertical, concave surface 46 facing inthe forward direction (arrow 34). The complex, modified scraper 40 wassaid to minimize turbulence.

However, Applicant's analysis of the complex modified scraper 40indicates that those advantages may be offset (i.e., substantiallyreduced) by many factors. One such factor is the movement of all of thescrapers 40 together (i.e., in the same direction at the same time).Applicant's analysis indicates that there is a tendency, for example,for undesired movement of the sludge in the return direction 36 due toall of the scrapers 40 moving together (at the same time in the returndirection 36), which tendency is also promoted by the one net 32attached to and moving with all of the blades. The undesired movement inthe return direction reduces the efficiency of the desired movement inthe “to” (or forward) direction.

Also, although the one net 32 is described in U.S. Pat. No. 5,431,818 asbeing pulled in the forward direction 34, and as being pulled in thereturn direction 36 (as by a spring), there are commercial embodimentsthat appear similar to the above-described system that uses the complexmodified scrapers 40. Those commercial embodiments have the one net 32reinforced and driven by a structural drive member (not shown) that hashigh resistance to both tension and compressive forces exerted parallelto the directions 34 and 36. Thus, in commercial practice, an extrastructural member has been used to apply respective “to” and “fro”forces to the one net 42 to cause the to and fro motion. Such an extrastructural member has increased the cost and weight of those commercialembodiments, and the extra weight increases the required energy (e.g.,electrical power and thus operating cost) to move the scrapers.

Applicant's analysis further indicates another disadvantage of thesubstantially oblique, convex surface 44 (or the right-triangularcross-section of the blades 30), in combination with all of the modifiedscrapers 40 (or all of the scrapers 30) moved together in the same “to”direction 34 and together in the “fro” direction 36 in the same timeperiods. As noted, this structure and movement results in undesiredmovement of the sludge in the return direction 36 due to all of thescrapers moving together (at the same time in the return direction 36).In an apparent attempt to reduce the undesired movement of the sludge inthe return direction 36, the U.S. Pat. No. 5,431,818 teaches use of ahigher speed for the return stroke than for the forward stroke (e.g., 12m/minute return vs., 3 m/minute forward). Such a higher speed returnstroke can agitate the particles of the sludge causing some of theparticles to be reintroduced into the liquid that was clarified by thesettler, for example. This further reduces the efficiency of the overalloperations because the reintroduced particles have to be again settledand then removed from the basin.

Applicant's analysis further indicates yet another disadvantage of allof the scrapers 30 or 40 moving together in the same “to” direction 34and together in the same “fro” direction 36 in the same time respectiveperiods. All of the prior push surfaces (e.g., 46) engage and push thesludge at the same time and are thus resisted by the sludge at the sametime. The requirement for higher power for this pushing of all bladestogether at the same time, and the increased weight of the extracompressive member that enables pushing instead of pulling thestructure, result in the motor used for moving the system being morecostly than a lower-power motor. Also, such extra compressive membermakes the net 32 less compliant with respect to uneven floors of thebasin, which in turn results in higher costs to initially provide asmoother floor for the basin (e.g., of concrete) and higher repair costsin not damaging the smoother floor of the basin during repair.

Lastly, if a generally-triangular cross-section blade is to be used,there is additional cost to manufacture the convex and concave shapes ofthe scrapers 40.

Accordingly, there is a need for a sludge system and methods that reducethe tendency of the sludge to be moved in the return direction 36 (suchtendency being caused by all of the scrapers moving together in the samereturn direction during a given time period). Further, there is a needfor such system and methods to avoid the need, in actual commercialpractice, for the use of any structural drive member other than the onenet (or a main frame) that supports (or carries) the blades themselves.Thus, there is a need in actual commercial embodiments to eliminate theabove-described extra structural drive member that has high resistanceto both tension and compressive forces exerted parallel to thedirections 34 and 36. Also, there is a need in actual commercialembodiments for the individual scrapers, or blades, to have aconfiguration manufacturable in a low-cost manner.

SUMMARY

Briefly, embodiments of the present invention meet all of the aboveneeds by providing a way of providing a sludge collector system andmethods that reduce the tendency of the sludge to be moved in the returndirection. Further, embodiments of the present invention meet all of theabove needs by providing a way for such system and methods to avoid theneed, in actual commercial practice, for the use of any structural drivemember other than the one net (or a main frame) that supports (orcarries) the blades themselves. Further, embodiments of the presentinvention meet all of the above needs by providing a way in actualcommercial embodiments to eliminate the above-described extra structuraldrive member that has high resistance to both tension and compressiveforces exerted parallel to the directions 34 and 36. Embodiments of thepresent invention further meet all of the above needs by providing a wayfor the individual scrapers, or blades, to have a configuration that ismanufacturable in a low-cost manner.

Embodiments of the present invention may meet all of the above needs byproviding two blades configured to be adjacent to each other; with adrive configured to simultaneously move each of the adjacent bladesrelative to an outlet of a basin, wherein the drive configuration is toprovide the simultaneous movement of each blade in opposition to theother blade. The embodiments may configure the drive with a firstsupport for one blade and a second support for the other blade, thesupports being separate from each other. The embodiments may furtherconfigure the drive with at least one direction-reversal unit connectedbetween the first and second supports.

Embodiments of the present invention may meet all of the above needs byalso providing a basin configured with adjacent first and second wallsintersecting the floor and intersecting each other to define a corner ofthe basin, where a first location of blade movement is next to thewalls, and a blade stop location is away from the walls, and a secondlocation is further away from the walls than the blade stop location.One blade is further configured with characteristics of flexibility andan extended shape so that when the one blade is in the first locationthe one blade is flexed and extends into the corner next to both of thewalls. The drive may be further configured to move the one blade fromthe blade stop location to the first location and cause the one blade toflex and extend into the corner so that the one blade is next to bothwalls and causes material near the walls to move from the walls andspill over the one blade and toward the blade stop location. The drivemay be further configured to move the one blade from the first locationto the blade stop location at the same time as the other blade is movedtoward the one blade so that the material spills over the other bladeand toward the second location.

Embodiments of the present invention may meet all of the above needs byalso providing a basin for moving sludge in a first direction relativeto a floor of a basin, in which a first blade is configured to extend atleast partly across the basin and a second blade is spaced from thefirst blade and configured to extend in spaced opposition to the firstblade. A drive may be configured to simultaneously move each of thespaced first and second blades along a common plane relative to thefloor of the basin in opposition to each other, the simultaneousmovement comprising the drive moving the first blade in the firstdirection and the drive simultaneously moving the second blade in asecond direction opposite to the first direction.

Embodiments of the present invention may meet all of the above needs byalso providing apparatus for moving sludge across a floor of a basinfrom a basin wall toward a sludge outlet. A plurality of blades maycomprise series of blades from a first blade to an nth blade, each bladebeing configured to extend at least partly across the basin in aparallel arrangement, the first blade being near the wall and the nthblade being toward the outlet. A first tensile member may carry a firstgroup of alternate ones of the blades in a plane adjacent to the floorso that odd number blades are carried by the first tensile member. Asecond tensile member may carry a second group of alternate ones of theblades in the plane adjacent to the floor so that even number blades arecarried by the second tensile member. A drive may be configured to onlypull on the first and second tensile members in a first direction sothat the respective first and second groups of alternate blades aremoved along the plane across the floor in the first direction, the pullon the first tensile member in the first direction alternating with thepull on the second tensile member in the first direction. A pulley maybe provided, and a tensile cable extends around the pulley and isattached to each of the first and second tensile members. The firsttensile member pulled in the first direction is effective to pull in thefirst direction on the tensile cable so that the pulled tensile cableacts around the pulley and pulls the second tensile member and therespective group of blades in the second direction in opposition to thefirst group of blades, blades of the first and second groups moving inopposition being effective to transfer sludge toward the outlet. Thesecond tensile member pulled in the first direction is effective to pullin the first direction on the tensile cable so that the pulled tensilecable acts around the pulley and pulls the first tensile member and therespective group of blades in the second direction in opposition to thesecond group of blades, blades of the first and second groups moving inopposition being effective to transfer sludge toward the outlet. Each ofthe blades may be configured with a cross section comprising a pushersurface and a receiver surface facing away from the pusher surface inthe second direction. The movement of each of the first and secondgroups of blades along the plane and in the opposite directions causestransfer of the sludge by the blades of the first group pushing thesludge in the first direction along the receiver surfaces of the bladesof the second group that are moving in the second direction. Pushing ofthe sludge spills the sludge in the first direction past the respectiveblades of the second group to provide spillover sludge adjacent to thepusher surfaces of the blades of the second group.

Embodiments of the present invention may meet all of the above needs byalso providing apparatus for moving sludge relative to a floor of abasin, in which a plurality of blades is configured to extend at leastpartly across the basin in an adjacent arrangement. A first tensilemember may move at least a first one of the blades adjacent to thefloor. A second tensile member may move at least a second one of theblades adjacent to the floor. The at least one first blade and the atleast one second blade may comprise a first blade adjacent to a secondblade. A drive may be configured to move the first and second tensilemembers and the respective first and second blades along the planerelative to the floor, movement including the first blade moving in afirst direction relative to the floor and in opposition to the secondblade and including the second blade moving in a second directionopposite to the first direction and in opposition to the first blade. Adirection-reversal mechanism may be between the first and second tensilemembers, the direction-reversal mechanism being actuated by the firsttensile member moving in the first direction to move the second tensilemember in the second direction, the direction-reversal mechanism beingactuated by the second tensile member moving in the first direction tomove the first tensile member in the second direction.

The way embodiments of the present invention avoid the need, in actualcommercial practice, for the use of any structural drive member otherthan the separate rails that carry the respective blades themselves, isby applying only tension, or pull, forces to each of separate rails, andby connecting one rail drive to each of the separate rails so that apull force applied to one rail in one (e.g., forward, or “to”) directionis applied by that rail (via the one rail drive) to the other rail inthe opposite (e.g., return, or “fro”) direction. In this manner, eachrail may be fabricated from material having minimum, or reduced,structural characteristics. Such material need have a characteristic ofhigh resistance only to tension forces, and need have low (or no)resistance to compressive forces. This characteristic greatly reducesthe cost of the sludge collection system, yet each rail is structurallysufficient to carry and drive the blades through the sludge as therespective rail moves across the bottom of the basin. As a result of thenew combination of the low-cost blades with the significantly improvedconfiguration of the drive, during the respective “to” and “fro”movements the blades resist those tension forces and the drive does notapply compressive forces to the rails. Thus, the present inventioneliminates the above-described prior extra structural drive member thathas high resistance to both tension and compressive forces.

The way of providing scrapers, or blades, that have a low-costconfiguration is by providing many low-cost blade embodiments, such asone using all-curved blades of standard configuration (such as acircular cross-section), or one using the blades shown in FIGS. 1A and1B, and in each case of low-cost blades using the low-cost blades in anew combination with a significantly improved configuration of the drivefor those low-cost blades.

Other aspects and advantages of the present invention will becomeapparent from the following detailed descriptions, taken in conjunctionwith the accompanying drawings, illustrating by way of example, theprinciples of embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be readily understood by thefollowing detailed description in conjunction with the accompanyingdrawings, wherein like reference numerals designate like structuralelements or operations.

FIGS. 1A through 1D describe two embodiments of prior art systems formoving material in a basin;

FIG. 2A is a plan view of a basin in which embodiments of the presentinvention may move material (e.g., sludge) by reducing a tendency in theprior systems for material to move in an undesired direction;

FIG. 2B illustrates two blades and blade motion details of an embodimentof the present invention to move sludge across the basin to an outlet;

FIG. 2C illustrates two blades and blade motion details of an embodimentof the present invention to move sludge from a corner of the basin;

FIGS. 3A and 3B illustrate blades and blade motion details of the FIG.2B embodiment;

FIGS. 4A, 4B, 4C, and 4D illustrate sludge movement structure of theFIG. 2C embodiment of the present invention;

FIGS. 5A, 5B, and 5C illustrate sludge movement structure of anotherembodiment of the present invention in which two sets of bladescooperate to move sludge toward one sludge outlet;

FIG. 6 illustrates sludge movement structure of another embodiment ofthe present invention in which two sets of blades cooperate to movesludge in opposite directions toward one central sludge outlet;

FIGS. 7A, 7B, 7C, and 7D illustrate embodiments of a drive of thepresent invention in which pull-only forces are applied to bladesmovable in each of first and second opposed directions to move thesludge in the first direction;

FIGS. 8A through 8C illustrate method operations for changing the sizeof spaces between adjacent blades of an embodiment of the presentinvention;

FIGS. 9A, 9B, 9C, 10, 11, 12, and 13 (with FIGS. 13A and 13B) illustrateembodiments of methods of the present invention.

Other aspects and advantages of embodiments of the present inventionwill become apparent from the following detailed descriptions, taken inconjunction with the accompanying drawings, illustrating by way ofexample, the principles of embodiments of the present invention.

DETAILED DESCRIPTION

Referring now to FIGS. 2A and 2B, embodiments 100 of the presentinvention may move material 102 in a first (or “to”) direction (seearrow 104) relative to a bottom (or floor) 106 of a basin 108. The firstdirection is a desired direction of material movement. The basin 108 maybe a container or tank provided with walls, e.g., four walls 109. Thewalls 109 may include two walls, a side wall 109L and an end wall 109E,that are adjacent to each other and that define a corner 109C (FIG. 2A)of the basin 108. The corner 109C is where the two walls 109L and 109Eintersect, and may extend vertically, for example.

The basin 108 may contain apparatus (not shown) in which the materials102 are collected. For example, the materials 102 may be collected bybeing separated from liquids (not shown) by plate or tube settlers (notshown) that promote settling of the material 102 to the bottom 106 ofthe basin 108. The apparatus may also be a flocculator (not shown) inwhich the materials 102 often inadvertently move to the bottom 106 ofthe basin 108. In each of the settler and flocculator examples, and inother equivalent apparatus, the materials 102 on the bottom 106 may bereferred to as sludge, as defined above. By the operation of suchsettler and flocculator apparatus, the sludge 102 settles on, andgenerally covers, the entire bottom 106 between the walls 109, and maybuild up to a depth above the bottom 106 of about twelve inches duringproper operation of the embodiments 100.

FIG. 2A shows areas on the bottom 106 along which embodiments 100 of thepresent invention may move the sludge 102. To enable clear illustration,the sludge 102 is shown in FIG. 2A covering only a small portion of thebottom 106, and the liquid is not shown. Also, to illustrate an area 1Aalong which an embodiment 100-1 (FIG. 2B) may move the sludge 102 in thefirst direction 104, FIG. 2A shows a width W as extending betweenopposite side walls 109L of the basin and a length L as extendingbetween the two other opposite end walls 109E of the basin. The area 1Ais defined by L times W. The sludge 102 may be moved across all or partof this area 1A by various embodiments of the present invention, e.g.embodiments 100-1, 100-3, and 100-4.

For descriptive purposes, FIG. 2A also shows lines identified by aletter and a number, e.g., “A1” and “B1”, and FIG. 2B shows lines “A1”,“B1”, “C1”, and “D1”. Each of these lines indicates one of variouslocations (or positions) at which structure of the embodiments of thepresent invention may be positioned during the operation of therespective embodiment, such that the exemplary “A1” for example isreferred to as a “position”.

Also, as to the corner 109C of the basin, it may be understood that insome basins, even though there are 90 degree angles between suchadjacent walls 109E and 109L, a sludge moving system (not shown) mayoperate to move the sludge 102 only from a circular area 2A within acircular perimeter P (shown in dashed lines) on the floor 106 of thebasin 108. The movement of the sludge 102 from the circular area 2Aleaves sludge in generally triangular areas TA (see dash-dash lines)that are defined by the adjacent walls 109E and 109L and by a portion ofthe perimeter P. As shown in FIG. 2C, an embodiment 100-2 of the presentinvention may be used to move sludge 102 from the triangular area TA, asdescribed below.

In a general sense, various FIGs. show the embodiments 100, eachconfigured with individual scraper elements, such as blades 110, andeach with at least two blades. As an overview, for example, in FIGS. 2B,and 3A-3B, two of the blades (110-1 and 110-2) are described withrespect to embodiment 100-1. In FIGS. 2C and 4A-4D, two of the blades(110-1 and 110-2) are described with respect to embodiment 100-2. InFIGS. 5A-5C exemplary numbers of such blades 110 are shown for anembodiment 101-3, one referred to as a first blade 110-1, anotherreferred to as a second blade 110-2, another referred to as a thirdblade 110-3, and another referred to as a fourth blade 110-4. Inembodiments 100-1 and 100-3, each such blade 110 is configured to movethe sludge in the direction 104, and each such blade 110 is shownconfigured to extend across the basin 108 between opposite walls 112 tomove sludge 102 generally across the area 1A of the basin 108. In anembodiment 100-2, each such blade 110 is configured to move the sludgein a direction 104C (FIG. 2A), which is away from the corner 109C andaway from the walls 109L and 109E to the perimeter P. A return directionof blade movement is identified as direction 114C. In an embodiment100-4 (FIG. 6), such blades 110 are grouped, with one group configuredto move sludge in the direction 104 (referred to as 104R), and anothergroup configured to move sludge 102 in an intended direction 104Lopposite to the one direction, so that the sludge may be moved, forexample, to a central location of a sludge outlet between the groups ofblades, as described below.

In each embodiment 100, as described below, one blade 110 moves inopposition to an adjacent blade 100, such that while one blade moves inthe desired direction 104 the other blade moves oppositely in the returndirection 114. With this in mind, also in a general sense, each blade110 may include structure to limit sludge movement in the returndirection 114. Such structure is initially described with respect to twoblades, blades 110-1 and 110-2 shown in FIGS. 2B, 3A and 3B. Referringto FIG. 3A, in a general sense, the blades 110 are configured with areceiver surface (RS) and a pusher surface (PS). The blades 110 may beof any configuration that fosters (or promotes or allows) “spillover”from RS to PS during the movement of the blades 110 in opposition toeach other. FIGS. 3A and 3B show a right triangular configuration, whichis referred to as an all straight-side blade configuration, with across-section defining a right triangle. Spillover is movement ortransfer of sludge 102 from a first side of the blade 110 (adjacent tothe RS) to a second side of the blade, the second side being opposite tothe first side and being the PS. Thus, the RS is at the first side andthe PS is at the second side. This sludge transfer (spillover) occursduring movement of two blades in opposition to each other.

In another exemplary blade configuration, FIG. 4A shows embodiment100-2, including all-curve blades 110 that may be configured with anoval cross section or a circular cross sectional configuration in whicha vertical plane divides the cross-section into the first side (see RS)and the second side (see PS). Each side has a substantially curvedsurface in that both RS and PS are curved. The exemplary circular crosssectional configuration includes two arcs (see exemplary arcs RS and PSthat identify part of a circle), as shown in FIG. 4A. Thus, for eachblade having the circular cross-section or the oval cross-section, thefirst and second sides, and related surfaces RS and PS, are adjacent toeach other in that there is no straight surface between the surfaces RSand PS. Embodiment 100-2 includes a height “h” of the blades 110 abovethe floor 106 of the basin that may be different (see h1 and h2),described below in connection with two blades 110-1 and 110-2 being inan “adjacent” arrangement.

In other exemplary blade configurations, FIGS. 1C and 1D show a compoundblade configured with a cross-section defining the first side 44 as afirst arc and the second side 46 as a second arc, where the arcs do notdefine the oval or circular cross-section, and where one arc is concaveand one arc is convex. In FIGS. 1C and 1D, the PS side 46 is concave andthe RS side 44 is convex.

It is to be understood that the embodiments 100 of the present inventionmay be used with any configuration of the blade 110 that fosters (orpromotes or allows) such “spillover” from RS to PS during the movementof the blades 110 in opposition to each other. The movement of theblades 110 in opposition to each other relates to an “arrangement” oftwo “adjacent” blades 110. All of the embodiments 100 have at least twoof the above-defined blades 110, and may have any number of such blades110 as may be necessary for the size of the basin 108 or for the rate atwhich the sludge 102 is to be moved, for example. When two blades 110are “arranged” to be “adjacent”, FIG. 2B shows that a first blade 110-1,for example, is on the left and a second blade 110-2, for example, is onthe right. The respective first and second blades 110-1 and 110-2 arenext to each other, which is spaced by a distance that is varied duringsludge transfer, the distance being in a range of from zero to fourinches, and this is referred to as being “adjacent to” each other, orbeing “adjacent blades”; thus there normally is no other “thing” (sludgepusher structure) between the two adjacent blades (there is only a spacecontaining sludge between the two adjacent blades 110-1 and 110-2).

In another general sense, as an example for movement of sludge 102 fromleft to right as viewed in FIG. 3A, the RS of each blade 110-1 and 110-2faces left (to receive sludge to be pushed to the right) and the PS ofeach blade 110-1 and 110-2 faces right (to push the sludge to theright); thus the PS of the first (left) blade 110-1 is next to the RS ofthe second (right) blade 110-2. It may also be understood that for thisexemplary sludge movement to the right, the (left) first blade 110-1 maybe referred to as a “rear” blade because, in the direction of sludgemovement 104, the rear blade 110-1 is “behind” the second blade 110-2,and the second blade 110-2 may thus be referred to as the “front” blade.In this example, the direction of desired sludge movement is 104.

In another general sense, as an example for movement of sludge 102 fromright to left as viewed in FIG. 6, a first blade 110-7 is on the rightand a second blade 110-6 is on the left. As an example for movement ofsludge from right to left, the RS of each blade faces right (see RS ofblade 110-6, to receive sludge to be pushed to the left) and the PS ofeach blade faces left (see PS of blade 110-6, to push the sludge to theleft onto RS of blade 110-5); thus the PS of the first (right) blade110-7 is shown next to the RS of the next (left) blade 110-6 in thisexample. It may also be understood that for this sludge movement to theleft, the blade 110-6 may also be referred to as a “rear” blade becausein the direction of sludge movement it is behind blade 110-5, and blade110-5 may be referred to as the “front” blade. In this example of FIG.6, with two desired directions, the directions of desired sludgemovement are shown as 104R to the right and 104L to the left for sludgemovement to the middle of the basin 108 at which a sludge outlet 160Cmay be located.

With this front and rear blade description in mind, in the all-curvedblade embodiment of FIGS. 2C and 4A-4D, the rear blade 110-1 isgenerally configured with the height h2 above the basin floor, height h2having a value that exceeds a height h1 of the front blade 110-2 toassure transfer of sludge 102 via spillover from the front of the rearblade 110-1 to the front of the front blade 110-2. Thus, the spillovermay be further defined as movement or transfer of sludge from a firstside of the front blade (adjacent to the RS of the front blade) to asecond side of the front blade (adjacent to the PS of the front blade),in which the second side is at the front of the front blade 110-2. InFIG. 4A, RS and PS are indicated by arcuate arrows that identify theextent of the respective receiving surface and pusher surface.

It may also be understood from the description below of FIG. 5B, forexample, that in embodiment 100-3 (when three or more exemplary blades110-1, 110-2 and 110-3 are arranged to be adjacent), a first blade 110-1is on the left and a second blade 110-2 is on the right of the firstblade 110-1 and a third blade 110-3 is on the right of the second blade110-2, as another example for movement of sludge from left to right indirection 104. For desired sludge movement from right to left in thedirection 104L (FIG. 6), first blade 110-7 is on the right, second blade110-6 is on the left of the blade 110-7, and third blade 110-5 is on theleft of the second blade 110-6, and the pusher surface PS of each suchblade 110-5 through 110-7 faces left.

One aspect of the first embodiment 100-1 is shown in detail in FIGS. 2B,3A and 3B. The two blades 110-1 and 110-2 are shown in FIGS. 3A and 3Bconfigured with the right triangle cross section. To provide theembodiment 100-1 with a characteristic of reducing a tendency of thesludge 102 to be moved in the return direction 114 described above withrespect to prior sludge collectors, a drive 116 (FIG. 2B) is configuredto move each of the spaced blades 110-1 and 110-2 simultaneously and intwo aspects of opposition to each other, including movement of the twoblades 110-1 and 110-2 toward each other, and movement of the two blades110-1 and 110-2 away from each other. This movement in opposition may bereferred to as “the blade movement”, and is used to described the twoblades 110-1 and 110-2, and to describe the other blades, e.g., 110-3through 110-7, for example. For ease of understanding, in FIG. 2B theportion of the drive 116 that moves the blade 110-2 is shown in solidlines, and the portion of the drive 116 that moves the blade 110-1 isshown in dot-dot-dash lines. The blades 110-1 and 110-2 move along acommon plane 118 (FIG. 3A) relative to the floor 106 of the basin 108.To provide such blade movement, the drive 116 may be configured with afirst support assembly (or rail assembly or slide assembly) 120, shownin solid lines. The first support assembly 120 is also referred to belowas a first tensile member in view of structural characteristics by whichthe first support assembly 120 is only pulled to move the blade 110-2alternately in the first direction 104 and then in the second direction114 and then back in the first direction, etc. The first supportassembly 120 may include two spaced first rails, or first tensile rails,122-1 and 122-2. The rails 122-1 and 122-2 are shown in FIG. 2B in solidlines, and extend parallel to each other, and the rails are spaced from,and generally parallel to, opposite walls 109L (FIG. 2A). The rails122-1 and 122-2 are connected to and support the blade 110-2. Theconnection is illustrated in FIG. 2B, for example, by small circlesoverlying the connected blades 110-1 and 110-2 and the rails 122-1 and122-2.

To further provide the blade movement, the drive 116 may be furtherconfigured with a second support assembly (rail or slide assembly) 124.The second support 124 is also referred to below as a second tensilemember in view of structural characteristics by which the second supportassembly 124 is only pulled to move the blade 110-1 alternately in thesecond direction 114 and then in the first direction 104 and then in thesecond direction, all in opposition to movement of the blade 110-2. Thesecond support assembly 124 may comprise two rails, or tensile rails,126-1 and 126-2. The rails 126-1 and 126-2 are shown in FIG. 2B, and toeasily distinguish from support 120 and rails 122-1 and 122-2, are shownin dot-dot-dash lines. The spaced second rails 126-1 and 126-2 extendparallel to each other and spaced from, and generally parallel to, thewalls 109L. The spaced second rails 126-1 and 126-2 are connected to andsupport the blade 110-2 (see similar circles over rails 126-1 and 126-2and blade 110-1).

The rails 122-1 and 122-2 are not connected to (and are thus separatefrom) the blade 110-1, and the rails 126-1 and 126-2 are not connectedto the blade 110-2, such that the blades 110-1 and 110-2 do not move inthe same direction (e.g., 104 or 114) during the same time period TP1,TP2, etc.

The movement of the blade 110-2 may be such that, during an exemplaryperiod of time TP1 during which the drive 116 moves the blade 110-1 inthe first direction 104 (for example), the drive 116 moves the blade110-2 in the second direction 114. The blade movement also occurs asfollows in relation to another exemplary time period TP2 that isimmediately later than the exemplary period of time TP1. During timeperiod TP2, the drive 116 moves the blade 110-1 in the second direction114, and the drive 116 moves the blade 110-2 in opposition to the firstblade 110-1 (i.e., in the first direction 104).

Still referring to FIG. 2B, in the embodiment 100-1 of the presentinvention, the drive 116 is configured with a first (or right as viewedin FIG. 2B) yoke, or pull-only unit, 128-1 connected to a firstpull-only drive cable 130-1 that is pulled by a pull-only drive motorsystem 131. The pull-only unit 128-1 is also connected to a right end ofeach of the first rails 122-1 and 122-2 of the first rail assembly 120.The first pull-only drive cable 130-1 only applies a tension, ortensile, force to the pull-only unit 128-1, which force is a pull in thefirst direction 104 and thus moves the blade 110-2 in the firstdirection 104.

The first rails 122-1 and 122-2, as well as the pull-only unit 128-1 andthe pull-only drive cable 130-1, may each have a characteristic of onlyhaving high resistance to a tension force (e.g., to a “pull” or“pulling” force), which is to say that the first rails 122-1 and 122-2,and the pull-only unit 128-1 and the pull-only drive cable 130-1 are notcapable of exerting any compressive force and are not capable ofresisting any compressive force. Thus, the pull-only drive cable 130-1cannot “push” on the first rails 122-1 or 122-2, and the first railscannot withstand any such “push”. The characteristic of the pull-onlydrive cable 130-1 includes having a tensile strength of about 10,000pounds, and no ability to withstand or exert any compressive force. Anexemplary rail 122-1 or 122-2 may be a thin member having a rectangularcross-section, such as a length of from about two inches to about threeinches, and a width of from about one-eighth inch to about one-quarterinch. The characteristic of the thin member includes having a tensilestrength in a range of from about 5,000 pounds to about 10,000 pounds.This may be referred to as a “given” tensile strength value. Thecharacteristic of such rail 122 also includes having no ability towithstand or exert any compressive force, which is also referred to ashaving a compression strength of a value substantially less than that ofthe given tensile strength value. It may be understood, therefore, thatthe rails 122-1 and 122-2 and the pull-only unit 128-1 and the pull-onlydrive cable 130-1 having these respective characteristics may bereferred to as “tensile members”.

The drive 116 is also configured to pull the second rail assembly 124 inthe first direction 104. For causing this aspect of the described blademovement of the blade 110-1, the pull-only drive motor system 131 isconfigured to pull on a second cable 130-2 that is connected to a yoke,or second pull-only unit, 128-2, which pulls on the second rails 126-1and 126-2 in the first direction 104. Each such pull-only cable 130-2,pull-only unit 128-2, and second rail 126-1 and 126-2 has the giventensile strength value which is sufficient to enable the respectivetensile member to respond to the pull of the drive 116 (e.g., of motorsystem 131) to cause the blade 110-1 to push the sludge 102 in the firstdirection. It may be understood, therefore, that each of the pull-onlycable 130-2, the pull-only unit 128-2 and the rails 126-1 and 126-2 mayalso be referred to as a “tensile member”.

As described above, blade movement in opposition to each other includesmovement of the two blades 110-1 and 110-2 toward each other, in whichone blade 110 moves in the return direction 114. To achieve this returnmovement, the drive 116 is configured with a two-part direction-reversalmechanism (or assembly) 132, one part being for the rail assembly 120and one part being for the rail assembly 124. For the first railassembly 120, a first (or right as viewed in FIG. 2B) direction-reversalyoke 134-1 is connected to a left end of each of the rails 122-1 and122-2 (solid lines). The direction-reversal yoke 134-1 is also connectedto one end of a direction-reversal cable 138. The cable 138 extends 180degrees around a direction-reversal unit, configured as an idler pulley,135 to an opposite cable end that is connected to a seconddirection-reversal yoke 134-2 connected to the rail 126-1 and rail126-2.

The rails 122-1 and 122-2 support the blade 110-2 for the blademovement, that is, support the blade 110-2 for the movementsimultaneously with and in opposition to the movement of the blade110-1. During blade movement in the first direction 104, thedirection-reversal assembly 132 operates so that the yoke 134-1 anddirection-reversal cable 138 pull on the direction-reversal yoke 134-2in the return direction 114. The yoke 134-2 pulls the rails 126-1 and126-2 for causing the return movement 114 of the rails 126 and the blade110-1. Each of the direction-reversal yoke 134-1 and direction-reversalcable 138 and direction-reversal yoke 134-2 may be referred to as atensile member in that each has the respective given tensile strengthvalue which is sufficient to enable the respective tensile member torespond to the drive 116 to cause the blade 110-1 to move in the returndirection 114 and push through the material 102 that is on the bottom106 of the basin 108. As described above, each such first tensile member122-1 and 122-2 and direction-reversal yoke 134-1, direction-reversalcable 138, and direction-reversal yoke 134-2 has a compression strengthof a value substantially less than that of the given tensile strengthvalue, such that the compression strength value is insufficient toenable the respective tensile member to respond to a push, for example apush attempting to cause the blade 110-1 to push material 102.

To effect the described blade movements, the drive 116 is alsoconfigured with the drive motor system 131. The motor system 131 causesthe pull-only cable 130-1 to pull in the one direction 104, e.g., duringalternate time periods, e.g., TP1, TP3, et seq. The motor system 131also causes the pull-only cable 130-2 to pull in the same one direction104, e.g., during other alternate time periods, e.g., TP2, TP4, et seq.,where the order of the time periods is TP1, TP2, TP3, etc. It may beunderstood that in response to each such pull in the first direction,one blade 110 is moved in the one direction while the direction-reversalassembly 132 causes the other blade 110 to move in the oppositedirection 114. In detail, in response to each such pull of the pull-onlydrive cable 130-1 in the first direction 104, blade 110-2 is moved inthe first direction 104 while the direction-reversal assembly 132 causesthe other blade 110-1 to move in the return direction 114. Also, inresponse to each such pull in the first direction 104 by the pull-onlydrive cable 130-2, the blade 110-1 is moved in the first direction 104while the direction-reversal assembly 132 causes the other blade 110-2to move in the opposite return direction 114.

In review, the drive 116 is configured to simultaneously move each ofthe spaced first and second blades, e.g., 110-1 and 110-2, along thecommon plane 118 relative to the floor 106 of the basin 108 inopposition to each other. The simultaneous movement includes the drive116 moving the first blade 110-1 in the first direction 104 and thedrive 116 (via the direction-reversal unit 135) simultaneously movingthe second blade 110-2 in the second direction 114 opposite to the firstdirection 104.

Embodiments of the motor system 131 are described below and noted asembodiments 131-1, 131-2, etc. The blade movement is first describedwith reference to FIGS. 3A and 3B (that are side views of FIG. 2B) andwith respect to the exemplary time periods. Time period TP1 extends froma time t0 to a time t1, time period TP2 extends from time t1 to a timet2, time period TP3 extends from time t2 to a time t3, and time periodTP4 extends from time t3 to time t4. Each time period TP has anexemplary duration that is substantially the same as every other timeperiod TP. Such duration may be selected from a range of about sixtyseconds to about one-hundred twenty seconds.

FIGS. 3A and 3B show exemplary positions of the blades 110-1 and 110-2at exemplary respective times t1 and t2. For clarity of initialdescription, these FIGS. do not show the sludge 102. FIG. 3A illustratesthat at t1 (the end of TP1) the blade 110-1 is at a left position A2 andthe blade 110-2 is at a right position B2. FIG. 3B illustrates that att2 (the end of TP2) blade 110-1 is at a right position A1 and blade110-2 is at a left position B1. For this exemplary pair of blades 110represented by blades 110-1 and 110-2, the positions A2 and B2 identifythe positions of the blades 110 in which the blades are spaced apart bya maximum distance MAX. An exemplary maximum distance MAX may be twice adistance D through which a blade 110 is moved during the respective timeperiod TP. Thus, for example, FIG. 3A may be described as showing theblade 110-2 at time t1 after that blade 110-2 was moved a distance D oftwo feet (from B1 to B2) in the forward direction 104. For anotherexample, in FIG. 3A the blade 110-1 is shown at time t1 after it wasmoved a distance D of two feet (from A1 to A2) in the return direction114. In these examples, at the time t1 the exemplary maximum distanceMAX may be four feet. In practice, each of the blades 110 may be movedthrough a distance D that is in a range of about two feet to about threefeet in either of the first direction 104 or the second direction duringone time period TP, such that the distance MAX may be from about fourfeet to about six feet.

FIG. 3B shows that for the same exemplary pair of blades 110 representedby blades 110-1 and 110-2, the positions A1 and B1 identify positions ofthe blades 110 spaced apart by a minimum distance MIN. An exemplaryminimum distance MIN may be zero inches, and may be in a range fromabout zero to about four inches. Thus, for example, FIG. 3B may bedescribed as showing the blade 110-1 at time t2 after moving in thefirst direction 104 an exemplary distance D of two feet from position A2to position A1. Also, FIG. 3B may be described as showing the blade110-2 at time t2 after moving an exemplary distance D of two feet in thereturn direction 114 from the position B2 to position B1. In thisexample, at the end of the time period TP2 the exemplary minimumdistance MIN is shown as having a value more than zero inches but lessthan about four inches.

Referring to FIGS. 2B and 3A, during the time period TP1 the motorsystem 131 may pull on the cable 130-1 (see solid lines) so thatpull-only unit 128-1 pulls the support assembly 120 in the firstdirection. The blade 110-2 moves in the first direction 104 (from B1 toB2). The direction-reversal assembly 132 reverses the direction of thecable 138 to move the blade 110-1 from position A1 to A2. The motorsystem 131 releases (does not pull on) cable 130-2, which is free tomove in the second direction 114 in response to pulling of thereverse-direction assembly 132. Thus, the rail assembly 120 moves in thesludge movement direction 104. The rail assembly 124 is pulled in thereturn direction 114 due to the rails 122-1 and 122-2 of the railassembly 120 pulling on the direction-reversal yoke 134-1 in the firstdirection 104, and due to the idler pulley 135 reversing the cable 138to act on the direction-reversal yoke 134-2. The rail assembly 124 (andblade 110-1) are thus pulled in the return direction 114 from positionA1 to A2. Thus, the blades 110-1 and 110-2 move away from each other tothe MAX spaced positions shown in FIG. 3A.

The next time period TP2 starts immediately after time period TP1.During the next time period TP2, the blades 110-1 and 110-2 are movedtoward each other to the respective positions A1 and B1 shown in FIG.3B. For these moves, the motor system 131 may pull on the cable 130-2(dot-dot-dash lines) and move the pull-only unit 128-2 in the firstdirection 104 and may release the cable 130-1 for movement in the seconddirection 114. During the time period TP2, the pull on the cable 130-2pulls the pull-only unit 128-2, which pulls the rails 126-1 and 126-2,which move the blade 110-1, all in the first direction 104. During thetime period TP2, the rails 126-1 and 126-2 pull on the reverse-directionyoke 134-2 in the first direction 104 and pull the drive member 138counterclockwise around the idler pulley 135 to cause a pull on thereverse-direction yoke 134-1 in the second direction 114. The pull onthe yoke 134-1 pulls on the rails 122-1 and 122-2, and the rails 122-1and 122-2 move the blade 110-2, all in the second direction 114. Thus,the blades 110-1 and 110-2 move toward each other during TP2 to the FIG.3B locations. In this manner, during each of the exemplary time periodsTP1 and TP2 the blades 110-1 and 110-2 move in opposition to each other.The action of the exemplary oppositely moving blades 110-1 and 110-2 onthe sludge 102 is described below.

FIGS. 3A and 3B also illustrate an exemplary cross-sectionalconfiguration of the blades 110-1 and 110-2, showing each of the firstand second blades having the exemplary low-cost, right triangular crosssection. Such cross section may include the pusher surface, or face, PS.The pusher face PS may extend perpendicularly relative to the rails 122or 126, and may have a height above the rails (e.g., above rails 122 or126) of from about one inch to about three inches, and in a preferredembodiment may have a height of 1.5 inches. The cross section mayinclude the receiver (or inclined or hypotenuse) surface RS tilted awayfrom the pusher face PS in the second direction 114. The surface RS isthus inclined relative to the plane 118. A base, or long side, 154 issecured to a respective one of the rails 122 and 126. The base 154 mayhave a length parallel to the respective first and second directions 104and 114 of from about two inches to about eight inches, and in apreferred embodiment may have a length of four inches. An orientation ofthe blades 110 may be defined in terms of a sludge push direction towardwhich the respective pusher faces PS are directed. One sludge pushdirection in the above description of FIG. 3A is the exemplary first (or“to”) direction 104. As noted in re FIG. 6, two sludge push directionsmay be provided. The above-described tilting of the inclined surface RSmeans that the surface RS is generally directed away from the sludgepush direction 104. The blades 110 having this three-part configurationmay be fabricated from flat stock material, which is relatively low incost as compared to curved stock material which may be used to fabricatethe curved structures 44 and 46 shown in FIGS. 1C and 1D, for example.

To illustrate the embodiment 100-2, reference is made to FIGS. 2A, 2C,4A, 4B, and 4C. FIG. 2A shows the arrow 104C indicating the desireddirection of sludge movement to move sludge from the corner 109C intothe area defined by the perimeter P, and shows the return direction114C. FIG. 4A shows the above-described all-curved cross sectionalconfiguration of the blades 110-1 and 110-2 of embodiment 110-2. Thisconfiguration may also be flexible as described below, so that theblades 110-1 and 110-2 conform to the configuration of the tensilemembers 122-3 and 126-3 described below for supporting the respectiveblades 110-1 and 110-2.

FIG. 2C shows a plan view of the blades 110-1 and 110-2 used inembodiment 100-2. Similar to all embodiments 100, in embodiment 100-2,blade movement in opposition to each other includes movement of the twoblades 110-1 and 110-2 toward each other, and movement in opposition toeach other also includes movement of the two blades 110-1 and 110-2 awayfrom each other, such that the above-described movement in opposition ofthe blades of embodiment 100-2 is also referred to as “the blademovement”. For support of the blade 110-2, an embodiment 120-2 of thefirst support assembly 120 is configured with a first tensile member122-3 having the above-described characteristic of transferring onlytensile forces. For support of the blade 110-1, an embodiment 124-2 ofthe second support assembly 124 is also configured with a second tensilemember 126-3 having a characteristic of transferring only tensileforces.

FIG. 4B shows that in the manner of the tensile rail 122 of the supportassembly 120, and of the pull-only unit 128-1 attached to the pull-onlydrive cable 130-1 (FIG. 2B), the first tensile member 122-3 isconfigured with a midpoint to which an embodiment of the pull-only drivecable 130 is attached (see 130-3). FIG. 4D shows that the drive cable130-3 extends around an idler pulley 155 to the pull-only drive motorassembly 131 that pulls on the cable 130-3 to move the tensile member122-3 in the return direction 114C. FIG. 4B also shows that in themanner of the tensile rail 126 of the support assembly 124, and of thepull-only unit 128-2 attached to the pull-only drive cable 130-2 (FIG.2B), the second tensile member 126-3 is configured with a midpoint towhich an embodiment of the pull-only drive cable 130 is attached (see130-4). The pull-only drive cable 130-4 extends around an idler pulley156 to the pull-only drive motor assembly 131 that pulls on the cable130-4 to move the tensile member 126-3 in the return direction 114C.

FIGS. 4B and 4C show that in the manner of the above-describeddirection-reversal mechanism 135, an embodiment of thedirection-reversal mechanism is configured with a first pulley 135-2-1and a second pulley 135-2-2. The first pulley 135-2-1 is configured toguide one end of the tensile member 122-3 to one end of the tensilemember 126-3 and to reverse direction. Also, this embodiment of thedirection-reversal unit is configured with the second pulley 135-2-2configured to guide the other end of the tensile member 122-3 to theother end of the tensile member 126-3 and reverse direction.

In view of this description, it may be understood that the drive 116 maybe described as being configured with an endless blade support cableextending around the first and second pulleys 135-2-1 and 135-2-2, inwhich there is defined a first section (the tensile member 122-3)extending between and on one side of the two pulleys 135-2-1 and135-2-2, and in which there is defined a second section (the tensilemember 126-3) extending between and on an opposite side of the twopulleys.

FIGS. 2C, 4B, and 4C, show that in the manner of the cable 130-2, thepull-only cable 130-3 only applies tensile forces to the tensile member122-3, and here the force is in the direction 114C, opposite to thedesired direction 104C. Similarly, the pull-only cable 130-4 onlyapplies tensile forces to the second tensile member 126-3 in thedirection 114C, opposite to the desired direction 104C.

FIG. 4A illustrates a vertical cross section of blades 110-1 and 110-2of embodiment 100-2. Each blade 110-1 and 110-2 is configured with theall-curve configuration, illustrated as circular, as may be exemplifiedby a hollow tube or a solid cylinder. The respective blade supports(tensile members 122-3 and 126-3) extend through the blades 110-1 and110-2 to move the blades as described below.

To provide the embodiment 100-2 with the characteristic of reducing atendency of the sludge 102 to be moved in the return (or “fro”)direction (arrow 114C) with respect to the corner 109C, the drive 116(FIG. 2B) is configured to move each of the spaced blades 110-1 and110-2 simultaneously and in opposition to each other. The blades 110-1and 110-2 move along the common plane 118 (FIG. 4A) relative to thefloor 106 of the basin 108. To provide such blade movement, the motorassembly 131 of the drive 116 only pulls on the pull-only driver cables130-3 and 130-4 because the cables 130-3 and 130-4, as well as thetensile members 122-3 and 126-3 may each have the above-describedcharacteristic of only having high resistance to tension forces (e.g.,to a “pull” or “pulling” force).

The tensile members 122-3 and 126-3 also have a characteristic offlexibility. This means that in response to a tension force (e.g., to a“pull” or “pulling” force) from the pull-only cable 130-3 or 130-4, therespective tensile members 122-3 and 126-3 bend, or flex, as shown inFIGS. 2C, 4B and 4C. In FIG. 4B, for example, the cable 130-4 has pulledthe member 126-3 into a bent configuration in which the member 126-3 isnear both of the walls 109L and 109E at a position Z1. In FIG. 4C, forexample, the cable 130-3 has pulled the tensile member 122-3 into a bentconfiguration in which the member 122-3 is at a blade stop position ZBSnear the member 126-3. In each case, the respective blades 110-1 and110-2 have also bent, or flexed, to conform to the configuration of therespective member. The pull on the member 122-3 in the return direction114C causes the flexible member 122-3 to flex generally at the point atwhich the pull-only driver 130-3 is attached to the member 122-3. Theresulting pull by the direction-reversing unit 135 causes the flexiblemember 126-3 to flex and tend to be straighter than shown in FIG. 4B,i.e., to be taut and to move in the desired direction 104C to becomealmost parallel to the member 122-3 at the blade stop position ZBS. InFIG. 4C, the member 126-3 is thus in a less bent (generally straight)configuration, i.e., with less bend than as shown in FIG. 4B.

With this blade movement in mind, FIG. 4B shows that the flexing ofmember 126-3 is a bending that stops with the blade 110-1 at theposition Z1 near the walls 109E and 109L. Referring to FIG. 4A, as theblade 110-1 approaches the wall 109E, sludge 102 that has been pushedtoward the wall 109E spills over the blade 110-1 and moves past theblade 110-1 in the desired direction 104C. The same action occurs atwall 109L. The members 122-3 and 126-3 being tensile members, each hasthe above-described respective given tensile strength value sufficientto enable the respective tensile member to respond to the drive 116 tocause the blade 110-1 to move in the return direction 114C and pushthrough the sludge 102 that is on the bottom 106 of the basin 108 in thecorner 109C, and to cause the sludge to spillover the blade 110-1, asdescribed above.

For causing another aspect of the described blade movement of the blade110-1, the drive 116 is further configured to move sludge 102 relativeto the floor from the location Z1, which is the location next to thewalls in one of the corners 109C of the basin. The drive 116 causes thesludge to move to the blade stop location ZBS (FIG. 2C) at which thereis spillover of sludge over the blade 110-2, and then causes movement ofthe sludge to a second location Z2 (FIG. 2C) away from the cornerfurther than position ZBS (to the perimeter P). To provide blademovement for such sludge movement, the drive 116 first only pulls on thepull-only driver cable 130-3. Under the pull-pull action of the drive116, the pull-only driver cable 130-3 pulls in the direction 114C on themember 122-3. The pull in the return direction 114C causes the flexiblemember 122-3 to flex generally at the point at which the pull-onlydriver 130-3 is attached to the member 122-3. The flexing is a bendingso that the member 122-3 and the blade 110-2 move toward the bladeposition ZBS. As the blade 110-2 moves toward the blade stop locationZBS, the member 122-3 and pulleys 135-2-1 and 135-2-2 of thedirection-reversal unit 135 pull on the member 126-3. The member 126-3becomes somewhat taut and moves in the desired sludge movement direction104C from the walls 109E and 109L toward the blade 110-2 and toward theblade stop location ZBS. The blade 110-1 moving in the direction 104Cpushes sludge 102 toward the blade 110-2 that is moving toward the blade110-1. The pull of the drive 116 on the pull-only driver cable 130-3thus causes the blades 110-1 and 110-2 to become adjacent to each otherat the blade stop location ZBS, with the tensile member 126-3 tautbetween pulleys 135-2-1 and 135-2-2. The blades cooperate to cause thesludge that has been pushed by the blade 110-1 toward the blade 110-2 tospillover the blade 110-2 and move past the blade 110-2 in the desireddirection 104C. The pull by the drive 116 stops. The drive 116 thenreverses.

Under the pull-pull action of the drive 116, now the pull-only drivercable 130-4 pulls in the direction 114C on the support 126-3 for causingthe previously-described movement of the blade 110-1, which is returnmovement 114C. The pull in the return direction 114C ends with the blade110-1 at the location Z1 near the walls 109C. FIG. 4B shows that as theblade 110-1 moves toward the location Z1, the member 126-3 and pulleys135-2-1 and 135-2-2 of the direction-reversal unit 135 pull on themember 122-3. The member 122-3 becomes taut and thus moves in thedesired sludge movement direction 104C toward the perimeter P. The blade110-2 pushes sludge 102 that has previously spilled over the blade110-2, and pushes sludge that is on the floor. The blade 110-2 pushesthis sludge in the desired direction 104C, and the sludge is thus movedto the location Z2, which may be within the perimeter P shown in FIG.2A. Pins 158 may be secured to the floor 106 to prevent the blade 110-2and tensile member 122-3 from extending into the perimeter P (FIG. 2A)to avoid interference with the sludge moving system (not shown,described with respect to FIG. 2A) that moves sludge on the area 2A ofthe perimeter P.

Based on this description, it may be understood that each of the members122-3 and 126-3 is configured with a first end and a second end. Themechanism 132 is at least one direction-reversal mechanism 132configured with at least one pulley 135-2-1, where mechanism 132 isconfigured with the two pulleys that are a first pulley 135-2-1 and asecond separate pulley 135-2-2. Also, there is at least the onedirection-reversal mechanism 132 that may also be configured with athird tensile member, that may be connected to the first end of thefirst member 122-3 and extend around the first pulley 135-2-1 and beconnected to the first end of the second support 126-3. The at least onedirection-reversal mechanism 132 may be further configured with a fourthtensile member, that may be connected to the second end of the firstsupport 126-3 and extend around the second pulley 135-2-2 and beconnected to the second end of the second support 126-3. As shown inFIG. 4B, for example, such third and fourth tensile members are therespective tensile supports 122-3 and 126-3. Each is one piece and isconnected to the other support as the respective supports extend aroundthe pulleys 135-2-1 and 135-2-2. Also, the first pull-only driver 130-3may be connected to the first support 122-3 and the second pull-onlydriver 130-4 may be connected to the second support 126-3.

Also based on this description, it may be understood that theconfiguration of a first blade 110-1 extends at least partly across thecorner 109C of the basin. Also, a second blade 110-2 is spaced from thefirst blade 110-1 and is further configured to extend a least partlyacross the corner 109C and in spaced opposition to the first blade sothat the first blade is closer to the corner 109C than the second blade110-2. Also, a first tensile member 126-3 is for the first blade 110-1,the first tensile member being configured with a first end and a secondend and connected to the first blade 110-1. Also, a second tensilemember 122-3 is for the second blade 110-2, the second tensile memberbeing configured with a third end and a fourth end and connected to thesecond blade 110-2. A first direction-reversal mechanism may beconfigured with pulley 135-2-1 as a first pulley and a length of cablemay be a first tensile connector connecting the first and third ends ofthe tensile supports 122-3 and 126-3. A second direction-reversalmechanism may be configured with pulley 135-2-1 as a second pulley and alength of cable may be a second tensile connector connecting the secondand fourth ends of the tensile members 122-3 and 126-3. The driver 116may be said to be further configured with a first pull-only driver(cable 130-4) connected to the first tensile support 126-3; and with asecond pull-only driver (cable 130-3) connected to the second tensilesupport 122-3. Also, the driver 116 actuates the first pull-only driver130-4 to pull the first tensile support 126-3 toward the corner 109C tothe first location Z1, and the pulled first tensile support 126-3 pullssuch first and second tensile connectors around the respective first andsecond pulleys 135-2-1 and 135-2-2 so that the second tensile support122-3 is pulled away from the corner and becomes taut at the secondlocation Z2 spaced from the first location Z1. Further, the driver 116actuates the second pull-only driver 130-3 to pull the second tensilesupport 122-3 from the second location Z2 toward the corner 109C to theblade stop location ZBS, and the second tensile support 122-3 is pulledby the second pull-only driver 130-3 that is effective to pull suchfirst and second tensile connectors around the respective first andsecond pulleys 135-2-1 and 135-2-2, so that the first tensile support126-3 is pulled away from the corner and toward the blade stop locationZBS. Also, driver 116 actuates the first pull-only driver 130-4 to pullthe first tensile support 126-3 toward the corner to the first locationZ1, with the pulled first tensile support 126-3 pulling the first andsecond tensile connectors around the respective first and second pulleys135-2-1 and 135-2-2 so that the second tensile support 122-2 is pulledaway from the corner 109C and becomes taut at the second location Z2spaced from the first location Z1. The drive 116 also actuates thesecond pull-only driver 130-3 to pull the second tensile support 122-3from the second location Z2 toward the corner 109C to the blade stoplocation ZBS, the second tensile support 122-3 pulled by the secondpull-only driver 130-3 being effective to pull the first and secondtensile connectors around the first and second pulleys 135-2-1 and135-2-2 so that the first tensile support 126-3 is pulled away from thecorner 109C and toward the blade stop location ZBS. Referring to FIG.4B, it may also be understood that the second tensile support 122-3pulled from the second location Z2 to the blade stop location ZBS andthe first tensile support 126-3 pulled away from the corner 109C towardthe blade stop location ZBS, are effective to transfer sludge 102SO fromthe first blade 110-1 over the second blade 110-2 and toward the secondlocation Z2. Further, the second tensile support 122-3 pulled by tensileforces around the pulleys 135-2-1 and 135-2-2 is moved from the bladestop location ZBS to the second location Z2 and is effective to causethe second blade 110-2 to transfer sludge 102SO to the second locationZ2.

The embodiment 100-3 is shown in FIGS. 5A through 5C, whichschematically illustrate a plurality of blades 110 provided as part ofthe configuration of each of the first rail assembly 120 (solid lines,FIG. 5A) and of the second rail assembly 124 (dot-dot-dash lines, FIG.5A). For example, the blades 110-2 and 110-4 are secured to the samefirst rails 122-1 and 122-2, such that the blades 110-2 and 110-4 form ablade array that moves in the same direction at the same time. Also, theblades 110-1 and 110-3 are secured to the same rails 126-1 and 126-2 andform a separate blade array such that the blades 110-1 and 110-3 move inthe same direction at the same time. The blades 110-1 and 110-3 may bedescribed as a set of blades, and the blades 110-2 and 110-4 describedas a set of blades that is separate from the set of blades 110-1 and110-3. Other embodiments of the present invention may have three or moreblades 110 in each such set, e.g., according to how far in the firstdirection the sludge 102 is to be moved before reaching a sludge outlet160 (FIG. 5C).

It may be understood from FIGS. 5A and 5B, for example, that therespective blades 110-1, 110-2, 110-3, and 110-4 are also arranged in aspaced sequence, shown as an exemplary sequence defined from left toright by the blade 110-1 followed by the blade 110-2 followed by theblade 110-3 followed by the blade 110-4.

In the configuration shown in FIG. 5A, the drive 116 is thus furtherconfigured with the first support assembly 120 connected to the blades110-2 and 110-4, and is configured with the second support assembly 124connected to the blades 110-1 and 110-3 (see small circles on rails126-1).

The above description of the blade 110-1 shown in FIG. 2B applies to thetwo blades 110-1 and 110-3 shown in FIGS. 5A through 5C. Further, theabove description of the blade 110-2 shown in FIG. 2B applies to the twoblades 110-2 and 110-4 shown in FIGS. 5A through 5C. Also, the abovedescription of the first support assembly 120, the second supportassembly 124, and the tensile rails 122 and 126 applies to the sameassemblies 120 and 124 and tensile rails 122 and 126 shown in FIGS. 5Athough 5C. Similarly, the above description of the drive 116 configuredwith the pull-only units 128-1 and 128-2, with the pull-only drivecables 130-1 and 130-2, and with the pull-only drive motor system 131,applies to the same structures shown in FIGS. 5A though 5C. The supportassemblies 120 and 124, the pull-only units 128-1 and 128-2, and thepull-only drive cables 130-1 and 130-2, are also referred to below astensile members in view of structural characteristics by which thesestructures are only pulled and may only be pulled. FIG. 5B shows theexemplary four blades 110-1 through 110-4 one after another and mountedon the respective tensile rails 126-1, 122-1, 126-1, and 122-1. It maybe understood then, that the drive 116 is configured to move the firstand second tensile members (the tensile rails 122 and 126) and therespective first and second blades 110-1 and 110-2) along the plane 118relative to the floor 106. That movement includes the first blade 110-1moving in the first direction 104 relative to the floor 106 and inopposition to the moving second blade 110-2, and the movement includesthe second blade 110-2 moving in the second (return) direction 114opposite to the first direction 104 and in opposition to the movement ofthe first blade 110-1. Also, FIG. 5A shows the direction-reversalmechanism (or assembly) 132 between the first and second tensile membersin that the assembly 132 is connected to the tensile members 122 and 126(and support assemblies 120 and 124) via the direction-reversal yokes134-1 and 134-2. In addition, it may be understood that thedirection-reversal mechanism 132 is actuated by the first tensile member122 moving in the first direction 104 to move the second tensile member126 in the second direction 114. The direction-reversal mechanism 132 isalso actuated by the second tensile member 126 moving in the firstdirection 104 to move the first tensile member 122 in the seconddirection 114. In review, the drive 116 is thus configured tosimultaneously move first and second members (the support assemblies 120and 124) so that at any time at least the blades (e.g., 110-1 and 110-2)of one first pair of alternating blades are moving toward each other andat least the blades (e.g., 110-2 and 110-3) of one different pair ofalternating blades are moving away from each other.

FIG. 5C illustrates the sludge transfer action of the exemplary fourblades 110-1 through 110-4 in the sludge 102 at the bottom 106 of thebasin 108. The sludge transfer action results from the above-described“blade movement” that includes the simultaneous and opposing movement ofthe respective spaced exemplary adjacent blades 110-1 and 110-2, or ofthe adjacent blades 110-2 and 110-3, or of the adjacent blades 110-3 and110-4, along the common plane 118 and in the opposite directions 104 and114. Each of these two adjacent blades may be referred to as a “pair” ofsuch blades 110, such that in FIGS. 5B and 5C, the following may bepairs of such blades: blades 110-1 and 110-2, blades 110-2 and 110-3,and blades 110-3 and 110-4, for example. In the diagram of FIG. 5C,columns are identified by brackets to indicate the corresponding blades110, e.g., 110-1. Positions A1, A2, B1, B2, C1, C2, D1, or D2 of certainblades are shown. A time t0-t4 is associated with one of five rows.Thus, each row represents the corresponding position of the blades atthe time corresponding to that row. For example, the time t0 in FIG. 5Ccorresponds to blade positions at the time t1 described with respect toFIG. 3A. In general, FIG. 5C shows that blade 110-1 moves in the forwarddirection 104 from position A2 to position A1, and moves in the reversedirection 114 from position A1 to A2; and corresponding blade movementsare shown for the other blades 110-2-110-4. In each case of the forwardblade movement in direction 104, the pull-only drive motor system 131 ofthe drive 116 pulls on the appropriate one of the pull-only drive cables130-1 and 130-2, and in each case of the return blade movement indirection 114, the direction-reversal mechanism 132 of the drive 116 atthe same time pulls on the appropriate one of the support assemblies 120or 124.

FIG. 5C shows that from time t0 to time t4 the blades are effective totransfer a batch of sludge 102 from position A2 into the sludge outlet160. In detail, during successive blade movements (e.g., duringexemplary time periods TP1, TP2, TP3, and TP4, the blade movements ofsuch pairs of blades causes transfer of the sludge 102 (sludge transferaction) only in the “to” direction 104 across the floor 106 of the basin108. FIG. 5C shows a sequence of such sludge transfer. This sequencestarts with exemplary sludge between blade 110-1 and blade 110-2 at anexemplary time t0. This sludge may, for example, have been pushed overthe blade 110-1 (from left to right), which is the above-describedspillover as the blade 110-1 moves to the left near the wall 109E. Blade110-1 then pushes sludge in direction 104 to spillover blade 110-2 inTP1, then blade 110-2 pushes sludge in direction 104 to spillover blade110-3 in TP2, then blade 110-3 pushes sludge in direction 104 tospillover blade 110-4 in TP3, then blade 110-4 pushes sludge indirection 104 into the sludge outlet 160 in TP4. In each case, the pushof sludge to spillover a blade is the above-described spillover.

In more detail, FIG. 5C shows sludge transfer that occurs during anexemplary time period TP1 when the blade 110-1 of the pair (110-1 and110-2) is moving in the first direction 104 and blade 110-2 of the pairis moving in the opposite direction 114. The blade 110-1 is initially(e.g., at time t0, in FIG. 5C) spaced by the distance MAX (FIG. 3A) fromthe blade 110-2 of that pair, with FIG. 5C showing sludge 102 in the MAXspace. During that time period TP1 the blade 110-2 is moved in theopposite direction 114 by the direction reversal mechanism 132 (FIG. 5A)operating in TP1 (starting at time t0). As shown in FIG. 5C by the t1row, such moving blade 110-1 has pushed an initial quantity of sludge102 in the first direction 104 along the reverse, or oppositely, movingreceiver surface RS (FIG. 5B) of the blade 110-2. That receiver surfaceRS was moving in the second direction 114. As indicated by arrow SO inrow t1, this pushing of that initial quantity of the sludge 102 in thefirst direction 104 caused some of the pushed sludge 102 to spill in thefirst direction 104 past the oppositely moving second blade 110-2 toprovide a quantity 102SO of sludge 102 to the right of blade 110-2,which is the spillover sludge. During at least a portion of the timeperiod TP1, the spillover sludge 102SO spills and is deposited adjacentto, and to the right of, the pusher surface PS of the second blade110-2. That spillover sludge 102SO may be said to be deposited in “frontof” the pusher surface PS of the second blade 110-2, in that the first(“to”) direction 104 is the desired direction of transfer of the sludge102. Further, because of this pushing action of the pusher surface PS ofthe first blade 110-1 in opposition to the receiver surface RS of theblade 110-2, the initial quantity of the sludge is not moved “backward”(i.e., is not moved in the undesired second direction 114) even thoughthe exemplary second blade 110-2 moves in the return (second, orundesired) direction 114. The configurations of the pusher surface PS ofthe first blade 110-1 moving in the first direction 104 and of theinclined receiver surface RS of the second blade 110-2 moving in theopposite direction 114 block (or restrict) the transfer of the sludge102 in the undesired second direction 114, which makes the desiredsludge transfer in the first direction 104 more efficient than thesludge transfer described above with respect to FIGS. 1A-1D.

FIG. 5C also shows that during TP1 the blade 110-3 moves in thedirection 104 with the blade 110-1, and moves to position C1. Row t1shows that by time t1 blade 110-3 has moved away from the blade 110-2,providing space between the blades 110-2 and 110-3 for reception of thespillover sludge 102SO. At the end of TP1, blade 110-1 is at positionA1, blade 110-2 is at position B1, and blade 110-3 is at position C1.

In TP2, drive 116, via pull-only drive cable 130-1, then moves blade110-2 from position B1 to position B2 in the first direction so thatblade 110-2 moves closer to the adjacent opposing blade 110-3 that ismoving in the second direction 114 under the above-described pull of thedirection reversal mechanism 132 (FIG. 5A) operating in TP2 (starting attime t1). In this manner, the blade 110-2 moving in the direction 104 toposition B2 (for example) limits an amount of the material 102 that theblade 110-3 moves in the second direction 114. Also, the blade 110-2pushes a spillover amount of sludge 102SO over and to the right of theblade 110-3 in a manner similar to that shown in FIG. 5C re blade 110-1pushing to the right.

FIG. 5C illustrates another exemplary pair of the blades 110, namelyblades 110-3 and 110-4. At the end of time period TP2 described above,the blades 110-3 and 110-4 are in the same relative positions (spaced bythe maximum distance MAX) as are shown in FIG. 3A with respect to blades110-1 and 110-2. FIG. 5C (at row t3) shows that during the next timeperiod TP3 (starting at time t2) the blade 110-3 is moved in the firstdirection 104 in opposition to movement of the blade 110-4 (which ismoved in the second direction 114). Thus, at the end of time period TP3blade 110-3 is shown at position C1 (its rightmost position) and blade110-4 is shown at position D1 (its leftmost position). FIG. 5C showsthat during time period TP3 the blade 110-3 deposited the spilloversludge 102SO to the right of the pusher face PS of the blade 110-4 inthe first direction 104. That spillover sludge 102SO to the right ofblade 100-4 includes the spillover sludge 102SO that was (during timeperiod TP1) deposited to the right of the pusher face PS of the blade110-2, and spillover sludge 102SO that was (during time period TP2)deposited to the right of the pusher face PS of the blade 110-3.

The next sludge transfer during the next time period TP4 may beunderstood by referring to FIG. 5C with respect to the blade 110-4. Uponreversal of the drive 116 and commencement of the time period TP4, theblade 110-4 is moved in the first direction 104 from position D1 to D2.The blade 110-4 (moving in the first direction 104) pushes in the firstdirection 104 the spillover sludge 102SO and other sludge 102 that is infront of the pusher face PS of the blade 110-4. That sludge is pushedinto the sludge outlet 160 for removal from the basin.

Thus, it may be understood that as a result of a sequence of exemplarytime periods TP starting from time t0, and through time periods TP1,TP2, TP3, and TP4, successive quantities 102SO of spillover sludge 102are moved in the desired first direction 104. This movement of thesludge 102 results in the sludge 102 being directed toward the sludgeoutlet 160 provided in the bottom 106 of the basin 108 for removal fromthe basin. Referring again to FIG. 5C, it is to be understood that thesludge shown in the rows corresponding to times t0-t4 is illustrative ofsequential pushing of the initial sludge 102 that was to the right ofthe blade 110-1 (at time t0), and that such sequential pushing continuesuntil that sludge is in the sludge outlet 160. It is to be furtherunderstood that there is generally sludge in front of each blade 110 andthat in any given TP one-half of the blades 110 are pushing sludge inthe forward direction 104, and the other one-half of the blades 110 arereceiving sludge on the front side of their respective pusher surfacesPS. Thus, the pusher surfaces PS of the blades 110-1-110-4 push sludgeinto the outlet 160 during every other time period TP.

By the above descriptions, it may be understood that the embodiments ofthe present invention provide apparatus for and methods of moving sludge102 relative to the floor 106 of the basin 108, and to the outlet 160 orto the perimeter P, for example. The apparatus may include a pluralityof blades, such as the exemplary blades 110-1 and 110-2, or the blades110-1 through 110-4, or more than four blades 110. The blades 110 mayeach be configured to extend at least partly across the basin 106 in aparallel arrangement, and are shown in FIGS. 2B and 5A extending theentire way across the basin 108, for example. Also, a first member mayinclude the first rail assembly 120 for carrying (i.e., supporting andmoving) a first group of alternate ones of the blades (e.g., the blades110-2 and 110-4) which are in the plane 118 adjacent to the floor 106. Asecond member may include the rail assembly 124 for carrying (i.e.,supporting and moving) a second group of alternate ones of the blades(e.g., the blades 110-1 and 110-3) in the plane 118 adjacent to thefloor 106. In this example, the drive 116 is configured tosimultaneously and oppositely move the respective first and secondmembers 120 and 124 and the respective first and second groups ofalternate blades along the plane 118 relative to the floor 106 of thebasin 108. The simultaneous and opposite movement is provided, forexample, when the first group of alternate blades (e.g., blades 110-2and 110-4) moves in the first direction 104 relative to the floor 106and in opposition to the blades 110-1 and 110-3 of the second group.Such movement includes the second group of alternate blades 110-2 and110-4 moving in the second direction 114 opposite to the first direction104 and in opposition to the first group.

In more detail, this movement of each of the first and second groups ofblades along the plane 118 and in the opposite directions 104 and 114causes transfer of the material 102 by the blades 110-2 and 110-4 of thefirst group pushing the material 102 in the first direction 104 alongthe receiver surfaces RS of the blades 110-1 and 110-3 of the secondgroup that are moving in the second direction 114. As a result, thepushed material 102 spills in the first direction 104 past therespective blades 110-1 and 110-3 of the second group to provide thespillover material 102SO adjacent to the pusher faces PS of the blades110-2 and 110-4 of the second group. It may be understood that the drive116 is configured to only pull on the first tensile member 122 and thenpull on the second tensile member 126, each pull being in the firstdirection 104. In one pull (e.g., on member 122) the first group ofalternate blades (e.g., 110-2, 110-4, etc.) is moved along the plane 118across the floor 106 in the first direction 104. In the next pull (e.g.,on member 126) the group of alternate blades (e.g., 110-1, 110-3, etc.)is moved along the plane 118 across the floor 106 in the first direction104. The pull on the first tensile member 122 in the first direction 104alternates with the pull on the second tensile member 126 in the firstdirection 104.

By the above descriptions, the following may be understood. Anembodiment of the present invention may provide each of the blades 110configured as a right triangle (FIGS. 3A and 3B) having a short (in theheight direction h) pusher side PS perpendicular to the common plane118, a long side 154 parallel to the plane 118, and a hypotenuse side(the receiver surface RS) inclined relative to the plane 118. In thisexample, each of the blades 110 has the short pusher side PS facing thedesired direction 104 of sludge movement. As a result, in the movementof a first group of blades (e.g., 110-1 and 110-3) in the desireddirection 104 (in opposition to the movement of a second group ofblades, e.g., 110-2 and 110-4, moving opposite to the desired direction104), the transfer of the sludge 102 is effected by the respective shortpusher sides PS of the respective first group of blades 110-1 and 110-3pushing the sludge 102 along the respective hypotenuses (surfaces RS) ofthe respective blades 110-2 and 110-4) of the second group. The pushingis to a front of the respective short pusher sides PS of the respectiveblades 110-2 and 110-4 of the second group of blades.

Still reviewing such descriptions, it may be understood that the drive116 is configured to operate to alternately cause such movement. Forexample, such movement may occur during one time period TP in which thefirst member 120 and the exemplary first group of alternating blades110-2 and 110-4 move in the first direction 104 relative to the floor106. Such movement may also occur during the same time period TP inwhich the second member 124 and the exemplary second group of alternateblades 110-1 and 110-3 move in the second direction 114 relative to thefloor 106.

The above-described spaced sequence of blades may be arranged in adifferent order (e.g., right-to-left as blades 110-1, 110-2, 110-3, and110-4) so long as the orientation of the blades 110 is suitably relatedto the desired direction of movement of the sludge 102. That is, in oneembodiment of the present invention there may be a blade orientationconfigured to move the sludge 102 in the “to” direction 104 to thesludge outlet 160, which in FIG. 5C is shown as being at the right endof the basin 108, with all of the blades 110 having the pusher surfacePS facing to the right (the direction 104). Many such blades 110, e.g.,four or six or eight, etc., may be used as described above.

Oppositely, another embodiment of the present invention may be used tomove the sludge 102 in the “fro” direction 114 to a sludge outlet 160that may be at the left end of the basin 108 (not shown). In this case,all of the blades 110 used for such purpose would have the pushersurface PS facing to the left (the direction 114). Again, many suchblades 110, e.g., four or six or eight, etc., may be used. In thisregard, referring to FIG. 6, another embodiment 100-4 of the presentinvention may be used when the sludge outlet 160 is at the center of thebasin 108, between the walls 109E, for example. For clarity ofillustration, the blades 110, the support assemblies 120 and 124, andthe drive 116 of this embodiment are as described above with respect toFIG. 2B, except as described below, and the blades 110 and the supportassemblies 120 are shown schematically as single lines. One section ofblades 110-1 through 110-3, for example, may be located to the left of acentral sludge outlet 160C. These exemplary blades 110-1 through 110-3may be configured with the respective pusher faces PS facing to theright as viewed in FIG. 6. The respective blades 110-1, 110-2, and 110-3may be arranged in the above-described spaced sequence, shown as anexemplary sequence defined from the far left of center to the near leftof center by the blade 110-1 followed by the blade 110-2 followed by theblade 110-3.

Another set of blades 110-5 through 110-7, for example, may be locatedto the right of the sludge outlet 160C. Each of these blades 110-5through 110-7 may be configured with the respective pusher faces PSfacing to the left as viewed in FIG. 6, and may otherwise be configuredthe same as the blades 110-1 through 110-3. That is, similar to thatdescribed above with respect to FIG. 2B, the blades 110-5, 110-6, and110-7 may be arranged in a spaced sequence, which may be an exemplarysequence defined from the far right of center to the near right ofcenter by the blade 110-7 followed by the blade 110-6 followed by theblade 110-5. The drive 116 may be configured with the first supportassembly 120 connecting the blades 110-2, 110-5, and 110-7, and with thesecond support assembly 124 connecting the blades 110-1, 110-3, and110-6.

With the above-described six blades 110-1 through 110-3, and 110-5through 110-7 in mind, it may be understood that the plurality of bladesrepresented by the six blades 110 may be configured to provide aplurality of desired sludge transfer (or push) directions (e.g., 104L,for a left direction in FIG. 6, and 104R, for a right sludge transferdirection in FIG. 6). For descriptive purposes, two groups of suchblades 110 may be defined. One group may be the blades 110-2, 110-5, and110-7, all of which are driven by the first support assembly 120. Asecond group may be the blades 110-1, 110-3, and 110-6, all of which aredriven by the second support assembly 124. Further, one may also definetwo pairs of blades 110 within each of these groups. The blades 110-1and 110-2 may form one pair; the blades 110-2 and 110-3 may form anotherpair, both of the first group. The blades 110-5 and 110-6 may form onepair; and the blades 110-6 and 110-7 may form another pair of the secondgroup. These blades 110-1 through 110-3 have the first orientation formoving the sludge in the sludge push direction 104R. For that purpose,the blades 110-1 and 110-3 move in opposition to the blade 110-2. Theblades 110-5 through 110-7 have the second orientation for moving thesludge in the sludge push direction 104L. For that purpose, the blades110-5 and 110-7 move in opposition to the blade 110-6.

With the blades 110-1 through 110-3, and 110-5 through 110-7 facing inthe described respective directions 104L and 104R, and connected to thedescribed respective support assemblies 120 and 124, the blades 110-1through 110-3 move the sludge 102 in the desired sludge transfer (orpush) direction 104R, and the blades 110-5 through 110-7 move the sludge102 in the desired sludge transfer (or push) direction 104L.

Again, many other numbers of such blades 110, e.g., four or six oreight, may be used for each such set, e.g., on each of the left andright sides of the outlet 160C, for example, as may be required for thelength L of the basin 108. In each example, the operation of the blades110 of each such set is as described above with respect to FIGS. 5Athrough 5C, for example, and serves to transfer the sludge 102 in therespective direction 104R or 104L, and to deposit the respective sludge102 into the exemplary sludge outlet 160C located at the center of thebasin 108.

Referring again to FIG. 2B, for example, it may be understood that oneembodiment of the drive 116 may be configured with the motor system 131having a shared-reel drive 131SR. Such shared-reel drive 131SR may bethe shared-reel drive described in U.S. Pat. No. 5,655,727, issued onAug. 12, 1997, and entitled “Sludge Collector Method and Drive WithShared Reel For Taking Up and Paying Out Cables”, the disclosure ofwhich is incorporated by reference. The shared-reel drive 131SR iseffective to pull on the cables 130-1 and 130-2 one at a time. Forexample, referring to FIG. 5A, in one operation (see TP2, FIG. 5C), thecable 130-1 connected to the pull-only unit 128-1 is taken-up on theshared-reel drive 131SR to move the blade 110-2 in the sludge movementdirection 104 from position B1 to B2. At the same time, the drive 131SRpays-out the second cable 130-2 at the same rate as the cable 130-1 istaken-up (pulled in). Cable 130-2 is connected to the pull-only unit128-2 so that the direction-reversal mechanism 132 pulls the blade 110-1in the opposite direction 114 from position A1 to A2.

The shared-reel drive 131SR reverses. In a reverse operation during TP3,the drive 131SR then takes-up (pulls on) cable 130-2 while paying-outcable 130-1. In the reverse operation, the pulled cable 130-2 moves thesupport assembly 128-2 and causes the blades 110-1, 110-3, etc., to movefrom their other positions back to their initial positions (e.g., theblade 110-1 from position A2 to position A1, FIG. 5C). At the same time,the drive 131SR pays-out the cable 130-1 at the same rate as the cable130-2 is taken-up. The payed-out cable 130-1 is connected to thepull-only unit 128-1, so that when the direction-reversal mechanism 132pulls, the blades 110-2, 110-4, etc. move in the opposite direction 114from position B2 to B1. The shared-reel drive 131SR then again reverses.The reversal occurs at the end of each time period TP.

Referring to FIGS. 7A and 7B, it may be understood that anotherembodiment of the drive 116 may be configured with the motor system 131having a dual-crank drive 131DC. The drive 131DC may include one crank170 mounted on a drive shaft 172 which is configured to rotate. Analternating rotary drive 173 rotates the shaft 172 through anappropriate number of degrees, and stops, and then reverses thedirection of rotation, and then stops, and reverses again, etc. Thecrank 170 is connected to one cable 174 and in one rotational directionpulls on the cable 174. A second crank 176 is also mounted on the driveshaft 172. The second crank 176 is connected to a second cable 178 andin an opposite rotational direction pulls on the cable 178. A pull bythe first crank 170 on the cable 174 occurs at the same time as thesecond crank 176 releases the other cable 178. A pull by the crank 176on the cable 178 occurs at the same time as the crank 170 releases theother cable 174. The cables 174 and 178 are secured to respectivepull-only cables 130-1 and 130-2 (FIG. 7B) to move the respectivesupport assemblies 120 and 124 as described above. The motor system 131DC also causes operation of the direction-reversal mechanism 132, asdescribed with respect to FIG. 2B, for example.

Alternatively, in another embodiment of the present invention, the drive116 may be configured with the dual-crank drive 131DC used with anotherembodiment of the direction-reversal mechanism 132 configured with anidler crank 135C as shown in FIG. 7C. The idler crank 135C rotates on anidler shaft 180. The one cable 138 of FIGS. 2B and 5A (extending aroundpulley 135) may be cut and the cut ends may be attached to opposite arms182 (FIG. 7C) of the idler crank 135C for operation in a manner similarto the idler pulley 135.

Referring to FIG. 7D, it may be understood that another embodiment ofthe drive 116 may be configured with the motor system 131 as amulti-cylinder drive 131MC. Idler shafts 190 mount a pair of spacedidler pulleys 192 and 194 for rotation. One idler pulley 192 guides thepull-only cable 130-1 from a first cylinder-piston motor 198 to thepull-only unit 128-1. The second idler pulley 194 guides the pull-onlycable 130-2 from a second cylinder-piston motor 202 to the pull-onlyunit 128-2. Actuation of one motor 198 pulls the cable 130-1 around theidler pulley 192 and pulls on the unit 128-1. Actuation of the othermotor 202 pulls the pull-only 130-2 around the idler pulley 194 andpulls on the unit 128-2. Actuation of the motors 198 and 202 alternates,with an un-actuated motor 198 or 202 releasing the respective pull-onlycable 130-1 or 130-2. Thus, a pull on the cable 130-1 occurs at the sametime as the second motor 202 releases the other cable 130-2. A pull onthe cable 130-2 occurs at the same time as the motor 198 releases theother cable 130-2. Thus, the cables 130-1 and 130-2 are moved in amanner similar to the cables 130-1 and 130-2 described above withrespect to FIG. 2B, for example. This embodiment of the drive 116 mayalso be used in conjunction with the direction-reversal mechanism 132,as shown in FIG. 2B, or with the idler crank 135C shown in FIG. 7C, forexample.

Referring to FIGS. 8A through 8C, and to FIG. 9A, an embodiment of thepresent invention may be illustrated as a method of moving the material102 along the floor 106 of the basin 108. Such method is illustrated ina flow chart 210 shown in FIG. 9A as including an operation 212 ofdefining a first space for a portion of the material 102 (e.g., sludge).The portion may be that part of the sludge 102 received between opposedones of the blades 110-1 and 110-2, and extending between opposite wallsof the basin, for example (FIG. 8A). The first space may be space 214(FIG. 8A) having a first volume that may extend across the basin andbeing adjacent to the floor 106. As a reference, the positioning of theblades 110-1 and 110-2 in FIG. 8A corresponds to the positioning shownin FIG. 3A of the blades 110-1 and 110-2, i.e., a maximum separationMAX. In regard to FIG. 5C, this maximum separation MAX may occur at theexemplary time t0, e.g., at the beginning of the exemplary time periodTP1.

The method moves to an operation 216 of reducing the size of the firstvolume of the first space. The reduced volume may be identified by 214Rin FIG. 8B and may extend across the basin. Operation 216 may beperformed by moving the pusher face PS relative to the receiver surfaceRS (FIG. 8B). The pusher face PS is a first vertical pusher of the firstblade 110-1, and the receiver surface RS is a first inclined pusher ofthe second blade 110-2. This relative movement is shown in FIG. 8Breducing the value of the first volume of the first space 214, and mayoccur in the next time period TP2, for example. Such reduction resultsin pushing the portion of the material 204. The portion corresponds tothe spillover sludge 102SO so that a first spillover volume 218SO-1(FIG. 8B) of the portion of the material 106 is pushed out of thereduced first volume (see arrow 102SO) and past the second inclinedpusher surface RS of blade 110-2 in the first direction 104. Thetransfer of the first spillover volume 218SO-1 in the first direction isthus complete, and the method is done.

Another aspect of the method of the present invention is shown in FIGS.8C and 9B, and includes a further operation 222 of a flow chart 224 inwhich the method of FIG. 9A is performed. As a preface to a nextoperation 226, FIG. 8B shows the first spillover volume 218SO-1 havingbeen pushed past the first inclined pusher surface RS and having entereda second space 226 having a second volume. The volume of the secondspace 226 is equal to the volume of the first space 214. The secondvolume of the space 226 (now identified by 226E in FIG. 8B) haspreviously become enlarged in the operation 226, e.g., by the motion ofthe blades 110-2 and 110-3 moving to respective positions B1 and C1(FIG. 5C) during TP1. Time t1 in FIG. 5C corresponds to the positionsbetween the blades 110-2 and 110-3 that provide the MAX distance. FIG.8C shows that the method of FIG. 9B may include the operation 228 ofreducing the size of a second volume of the second space 226 (nowidentified as 226R in FIG. 8C). The volume of the second space 226E isreduced by moving the blade 110-2 in the first direction 104 and theblade 110-3 in the second direction 114. A vertical pusher surface PSattached to the inclined pusher surface RS of the blade 110-2 thus movestoward the blade 110-3, thus toward the inclined pusher surface RS andtoward the third vertical pusher surface PS of the blade 110-3. Thesemovements of the blades 110-2 and 110-3 are into (and reduce) the secondvolume of the second space 226E (FIG. 8B) to form the reduced space226R. These movements are effective to push (see dashed arrow 102SO,FIG. 8C) a second spillover volume 218SO-2 of the material 102 past thethird vertical pusher surface PS (of the blade 110-3) in the firstdirection 104 and out of the second volume of the second space 226R andadjacent to (and in front of) the third vertical pusher surface PS ofthe blade 110-3, and the method is done.

Referring to FIGS. 2C, 4A through 4D, and to FIGS. 9A and 9B, anembodiment of the present invention may be illustrated as a method ofmoving the material 102 along the floor 106 of the basin 108 from thecorner 109C. Such method is also illustrated in the flow chart 210 shownin FIG. 9A and the flow chart 224 shown in FIG. 9B. The operation 212may define a first space for a portion of the material 102 (e.g.,sludge). Referring to FIG. 4C, the portion may be that part of thesludge 102 received between the one blade 110-1 and the corner walls109E and 109L of the basin, for example. The first space may be space300 (FIGS. 4A & 4C) shown having a first volume and being adjacent toand above the floor 106 and extending from the blade 110-1 to the cornerwalls 109E and 109L.

The method moves to the operation 216 of reducing the size of the firstvolume of the first space. The reduced volume is identified by 300R inFIGS. 4A & 4B. Operation 216 may be performed by moving the pusher faceRS of blade 110-1 relative to (i.e., toward) the walls 109E and 109L(FIG. 4B), also shown in FIG. 4A with respect to wall 109E. As describedabove with respect to FIG. 4A, as the blade 110-1 approaches the wall109E (which is also exemplary of the blades moving toward the wall109L), sludge 102 that has been pushed toward the wall 109E spills overthe blade 110-1 (see arrow SO) and moves past the blade 110-1 in thedesired direction 104C (and is shown as 102SO, FIG. 4A). In terms ofoperation 216, there is a second space 302 between the blade 110-1 andblade 110-2 (FIGS. 4A & 4B).

The method moves to flow chart 224 (FIG. 9B). Having done operation 222,the method moves to operation 226 in which the second space 302 isdefined. The second space 302 is shown having a second volume definedfrom adjacent to and above the floor 106 and extending from the blade110-1 to the blade 110-2. With the blade 110-1 at the position Z1 andblade 110-2 at position Z2, space 302 is large relative to space 300R(FIG. 4A). The method moves to operation 228. Referring to FIG. 4C foran understanding of this operation, the second space 302 has becomereduced (shown as 302R2) in that blade 110-1 has moved away from thewalls 109E and 109L and blade 110-2 has moved from position Z2 to ZBS.Such reduction results in pushing the portion 102SO of the material 204away from the walls and toward the blade 110-2 that is at the same timemoving toward the walls (toward position ZBS). The portion correspondsto the spillover sludge 102SO (plus other sludge). The portion is pushedout of the reduced second volume 302R2 and past the second blade 110-2in the first direction 104C. This aspect of the method is done.

Another aspect of the method of the present invention is shown in FIGS.8C and 9C, and includes an operation 230 of the flow chart 232.Operation 230 repeats the respective operations of flow chart 210 (FIG.9A). Thus, there is an alternating reducing of the first and secondvolumes of the respective spaces 214 and 226. The repeating alternatelyoccurs so that the first volume of the first space 214 is reducedsimultaneously with an enlarging of the second volume of the secondspace 226, and the second volume of the second space 226 is reducedsimultaneously with an enlarging of the first volume of the first space214. The operation 230 is performed with respect to as many of thespaces as are necessary to transfer the sludge 102 to the outlet 160.For example, FIG. 8A shows four blades 110. Between those blades twospaces 214 and one space 226-R are defined and the sludge 102 istransferred from the blades 110-1, 110-2, 110-3, and 110-4 to the outlet160. Thus, three exemplary spaces are provided in this exemplaryoperation 230. Other numbers of spaces may be provided depending on thesize of the basin and the value of the distance D (FIG. 3A) throughwhich the blades 110 are moved. These operations result in sludgetransfer in the sludge transfer direction 104, as indicated by thespillover volumes 218SO-1 and 218SO-2, for example (FIGS. 8B and 8C).When the desired amount of sludge 102 is transferred to the sludgeoutlet 160, the method is done.

Referring to FIGS. 2C, 4A through 4D, and to FIG. 9C, another embodimentof the present invention may be illustrated as another aspect of amethod of moving the material 102 along the floor 106 of the basin 108from the corner 109C. The other aspect also includes the operation 230of the flow chart 232. Operation 230 repeats the respective operationsof flow charts 210 and 224. Thus, there is an alternating reducing ofthe first and second volumes of the respective spaces 300 and 302. Therepeating alternately occurs so that the first volume of the first space300 is reduced (FIGS. 4A & 4B, space 300R) simultaneously with theenlarging of the second volume of the second space 302 (FIG. 4B). Thismay occur as blade 110-1 moves to position Z1. Also, in the same timeperiod TP in which space 300 was reduced to 300R (FIGS. 4A & 4B), FIG.4C also shows that there is a third space 304 in front of the blade110-2 toward the perimeter P as blade 110-2 moves in direction 104C toposition Z2. Operation 230 is performed by so moving both the blade110-1 toward the walls to position Z1 and moving the blade 110-2 to theperimeter P to position Z2 so that the spillover sludge 102SO from thewalls (and now in front of blade 110-2) is moved to the perimeter P.FIG. 4B shows this spillover sludge 102SO inside the perimeter P. Whenthe desired amount of sludge 102 is transferred from the walls toperimeter P, the method is done.

Another aspect of the method of the present invention is shown in FIGS.4B, 4C, 4D, 5C, and FIG. 10, which shows a flow chart 242. The methodmoves sludge 102 from a first location (e.g. A2, FIG. 5C, or Z1, FIG.4B) in the settler basin 108 to a second location (e.g., outlet 160,FIG. 5C, or perimeter P, FIG. 4B) in the settler basin. The respectiveexemplary first and second locations A2 and 160, or Z1 and P, are spacedin the first direction 104. This method may include an operation 244 ofpushing some of the sludge 104 from the first location A2, which may beperformed during a time period TP 1. The pushing is in the firstdirection 104. At the same time as operation 244 is performed, themethod performs an operation 246. In operation 246 the receiver surfaceRS of blade 110-2 is moved opposite to the first direction 104 (i.e., ismoved in the second direction 114) and into the sludge 102 that is beingpushed during operation 244. A result of operations 244 and 246 is thata portion of the sludge that is pushed in the first direction 104 ispushed onto and over, or past, the receiver surface RS of blade 110-2 sothat the portion is moved toward the second location 160.

In respect to FIG. 4B, operation 244 may be performed by the blade 110-1moving from position Z1 to position ZBS, and operation 246 may beperformed by blade 110-2 moving from location Z2 to position ZBS. Asdescribed above, these movements of blades 110-1 and 110-2 result insludge 102SO spilling over to the right of blade 110-2 as viewed in FIG.4C at position ZBS.

Another embodiment of the method of flow chart 242 (FIG. 10) is to movethe sludge 102 further along the floor 106 of the settler basin 108 inthe first direction 104. The method may include an operation 252performed in a second time period TP2 following the first time periodTP1. The blade 110-2 (FIG. 8A) is configured elongated with aright-triangular configuration so that a pusher surface PS and areceiver surface RS meet at an acute angle. Operation 252 moves theblade 110-2 in the first direction 104 to move the pusher surface PS andfurther push the sludge in the first direction. FIGS. 8B & 8C show thismovement of blade 110-2 to position B2. The method moves to an operation256 in which receiver surface RS of a third blade 110-3 is opposite andadjacent to the pusher face PS of the blade 110-2. In operation 256 theblade 110-3 is moved in the second direction 114 so that the pusher facePS of the moving blade 110-2 pushes some of the sludge onto and over thereceiver surface RS of the blade 110-3, and the method is done. FIGS. 8B& 8C show this movement of blade 110-3 to position C2.

The operation 252 of flow chart 242 may also be illustrated by referenceto FIGS. 4A & 4B. Operation 252 may occur in TP2 with the pusher surfacePS of blade 110-2 moved in the direction 104C further away from thewalls 109E and 109L. Such further movement of the blade 110-2 is by thepull-only cable 130-4 pulling on the tensile member 126-3 to render thetensile member 122-3 taut between the pulleys 135-2-1 and 135-2-2. Thisfurther movement of blade 110-2 is shown as movement from the positionZBS to position Z2 (FIG. 4B).

Another embodiment of the method of the present invention relates toflow chart 260 shown in FIG. 11. Spaces between blades (shown in FIGS.8A-8C) are referred to in operation 264 of flow chart 260. In anoperation 261, each of two blades is provided with pusher and receivedsurfaces. These may be exemplary blades 110-2 and 110-3 shown in FIG.8A, for example, having the elongated right triangular cross sectionconfiguration. The method moves to operation 262 in which the two bladesare arranged parallel with the pusher surface PS of one blade facing thereceiver surface RS of an adjacent blade. The exemplary blades 110-2 and110-3 are shown so arranged in FIGS. 5A & 8B (surfaces facing). Themethod moves to operation 264 and the blades are moved relative to eachother. This may be as shown in FIGS. 8B and 8C, where the moving of theblade 110-2 is in the first direction 104 and then in the seconddirection 114, and the blade 110-3 is moving oppositely to each suchdirection. The moving makes the space 226 defined between these twoblades 110-2 and 110-3 alternately smaller (226R) and larger (226E). Asa result, the pusher surface PS of the blade 110-2 further pushes thesludge in the first direction 104 as the space is made smaller, and someof the sludge pushed in the first direction 104 is pushed onto and over,or past, the receiver surface RS (past the blade 110-3, FIG. 8C), andthe method is done.

In other embodiments of this method of FIG. 11, the providing operation261 may provide two additional blades 110-3 and 110-4 (FIG. 8A). Each ofthe additional blades 110-3 and 110-4 may also be configured elongatedwith a right-triangular cross-sectional configuration so that a pushersurface PS and a receiver surface RS meet at an acute angle. Thearranging operation 262 also arranges the additional two blades 110-3and 110-4 in parallel relationship with the pusher surface PS of theblade 110-2 being opposed to the receiver surface RS of the additionalblade 110-3 to define another large space 214E (FIG. 8B). During theoperation 264 of causing relative movement to make the space 214Esmaller as in FIG. 8B (see 214R), the opposed blades 110-3 and 110-4move closer together and are effective to move the sludge 102 across andpast the receiver surface RS of the blade 110-4 (FIG. 8B, 102SO-2). Thedrive 116 reverses and the blades 110-3 and 110-4 are moved to thepositions shown in FIG. 8A so that the space 214R becomes larger again(see 214E, FIG. 8A), and the method is done.

The operation 261 of flow chart 260 may also be illustrated by referenceto FIGS. 2C, 4A, 4B and 4C. Another embodiment of operation 261 may beto provide the all-curved blades 110-1 and 110-2 shown in FIG. 4A havingthe receiver and pusher surfaces RS and PS respectively. Operation 262may be performed as shown in FIGS. 2C and 4C with the blades beinggenerally parallel with receiver surface RS of blade 110-2 opposite topusher surface PS of blade 110-1. The referenced space is 302 (FIG. 4B)between the two blades. Operation 264 is performed in theabove-described manner with the space 302 having a maximum value asshown in FIG. 4B and a minimum value 302R2 as shown in FIG. 4C, 302R2indicating a reduced value of space 302 identified as reduced byreference 302R. The drive 116 reverses and the space 302 is as shownlarger in FIG. 4B, and the method is done.

Another embodiment of the method of the present invention is shown inFIG. 5A, and in FIG. 12 which shows a flow chart 270. This method movessludge 102 along the floor 106 of the basin 108. The method moves to anoperation 272 which provides a first tensile structure, such as thefirst rail assembly 120 and first rails 122-1 and 122-2 (FIG. 5A), witha first group of sludge mover blades, such as blades 110-2 and 110-4,adjacent to the floor 106. The method moves to an operation 274 ofproviding a second tensile structure, such as the second rail assembly124 and second rails 126-1 and 126-2 (FIG. 5A) with a second group ofsludge mover blades 110-1 and 110-3 adjacent to the floor 106. Each suchgroup is in a spaced configuration. The blades 110-2 and 110-4 of thefirst group alternate with the blades 110-1 and 110-3 of the secondgroup in the common plane 118 adjacent to the floor 106. Other numbersof blades 110 may be provided in each group, such as the four shown inFIG. 5C.

The method moves to an operation 276 of connecting a cable, such as thereverse-direction cable 138, to common ends of a first tensile structure(e.g., 122-1 and 122-2) and a second tensile structure (e.g., 126-1 and126-2). The cable 138 may be secured to pull-only yokes 134-1 and 134-2.The cable 138 is connected to the direction reversal mechanism 132(FIGS. 5 a & 7D) to reverse the direction of the cable 138.

The method moves to an operation 280 of pulling on the first tensilestructure (which may be via the drive 116 and pull-only yoke 128-1) tomove the first tensile structure 122-1 and 122-2 and the first group ofsludge mover blades 110-2 and 110-4 in the first direction 104. Thefirst tensile structure 122-1 and 122-2 pulls on the direction-reversingyoke 134-1, which pulls on cable 138. Mechanism 132 reverses directionof the cable 138, which pulls on the second tensile structure 124 tomove the second group of sludge mover blades 110-1 and 110-3 in thesecond direction 114 opposite to movement of the first group of sludgemover blades 110-1 and 110-3. The moving groups of blades 110-1 through110-4 move the sludge 102 along the floor 106 in the first direction104.

The method moves to an operation 282 of pulling on the second tensilestructure to move the second group of sludge mover blades 110-1 and110-3 in the first direction 104. The pulling may be by pulling thepull-only drive cable 130-2 so that the tensile structure 124 pulls onthe cable 138 and the reversed direction portion of cable 138 pulls onthe tensile structure 120 to move the first group of sludge mover blades110-2 and 110-4 in the second direction 114 opposite to this movement104 of the second group of sludge mover blades 110-1 and 110-3. Themoving groups of blades 110-1 through 110-4 continue to move the sludge102 along the floor 106 in the first direction 104.

Also based on this description of the embodiment of FIG. 12, it may beunderstood that such embodiment may be used to move sludge from thecorner 109C. FIG. 4B shows the first location Z1 in the basin 108 is inthe corner 109C defined by the intersection of the two adjacent walls109E and 109L of the basin. The second location Z2 is away from thosewalls and out of the corner 109C. With this in mind, to move sludge outof the corner, the operations 272 and 274 provide the respective tensilemember 126-3 and 122-3. Also, in operation 276 there is a mounting of afirst pulley (e.g., 135-2-1, FIG. 4B) against one of the walls (e.g.,109E) and spaced from the corner 109C. Also, a second pulley (e.g.,135-2-2, FIG. 4B) is mounted against the other of the walls (e.g., 109L)and spaced from the corner. Also, the connecting of operation 276 may beby connecting members 122-3 and 126-3 to extend around those first andsecond pulleys for direction reversal. Thus, (FIG. 4C) a first sectionmay be configured as the tensile support 122-3 with a blade 110-2. Asecond section may be configured as the tensile support 126-3 with blade110-1. With this configuration, the nomenclature of the directions isreversed, with 114C being a first direction and 104C being a seconddirection. Operation 280 results in pulling on the first section 122-3in a first direction 114C opposite to the second direction 104C, causingthe reversed second section (tensile support 126-3) in the seconddirection 104C and the blade 110-1 to push some of the sludge from thefirst location Z1 toward the second location Z2, the pushing being inthe second direction 104C and onto the first blade 110-2. Also, pullingon the first section 122-3 is effective to move the first pusher (blade110-2) in the first direction 114C opposite to the first direction 104Cinto the pushed sludge (pushed by blade 110-1, FIG. 4C). The pushing ofsome of the sludge by the second section (tensile support 126-3) iseffective to push some of the sludge in the second direction 104C pastthe first section (tensile support 123-3) and past the pusher (blade110-2) toward the second location Z2. Operation 282 then results inpulling on the second section 126-3 in the first direction 114C sodirection reversal pulls the first section 122-3 taut (FIG. 4B) in thesecond direction 104C to cause the blade 110-2 to push the sludge 102S)to the perimeter P.

Another embodiment of the method of the present invention is shown inFIGS. 2C, 4A through 4C, and in FIG. 13 which shows how FIGS. 13A and13B combine to show a flow chart 320. This embodiment moves sludge 102out of the corner 109C of the basin, and is described in terms of anendless loop 328 shown in FIGS. 2C, 4B and 4C. The method moves tooperation 322 of providing a first tensile structure connected to afirst sludge mover blade adjacent to the floor. The first structure maybe tensile support 126-3 with blade 110-1, FIG. 4B. The method moves tooperation 324 of providing a second tensile structure connected to asecond sludge mover blade adjacent to the floor. The structure may betensile support 122-3, with blade 110-2, FIG. 4B. The first and secondblades 110-1 and 110-2 are adjacent to each other in the common plane118 that is adjacent to the floor 106. The method moves to operation 326of connecting the first and second tensile structures to each other.Operation 326 may result in defining the endless loop. The loop may bethe loop 328 identified at four places along the endless extent of theconnected supports 126-3 and 122-3 (see FIGS. 2C, 4B & 4C. The loop 328is defined by the connected supports 122-3 and 126-3. The method movesto operation 330 of extending the loop around spaced pulleys, a firstpulley being adjacent to a first of the walls and a second of thepulleys being adjacent to a second of the walls. The spaced pulleys maybe respective first and second pulleys 135-2-1 and 135-2-2 and the loopmay be loose around the pulleys to define slack in the loop. The firstpulley may be adjacent to a first of the walls (e.g., 109E) and thesecond pulley may be adjacent to a second of the walls (e.g., 109L). Theslack in the loop 328 is shown, for example, in FIG. 4B in that whilethe support 122-3 is tight or taut between the pulleys 135-2-1 and135-2-2, the length of the support 126-3 between the pulleys (i.e., fromthe pulleys to the walls 109E and 109L) is in the above-described bent(or flexed) configuration that has a greater value than the distancebetween and around the pulleys. For ease of illustration, this value isnot shown to scale. The method moves to operation 332 of pulling on thefirst tensile structure toward the walls to move the first sludge moverblade into the corner to push sludge against the walls and over thefirst sludge mover blade away from the walls. The pulling tightens theslack, as shown in FIG. 4B where the pulled first tensile structure126-3 is shown pulling tightly around the pulleys and on the secondtensile structure 122-3, tightening the slack and moving the secondsludge mover blade 110-2 away from the first sludge mover blade 110-1.This pulling moves the first sludge mover blade 110-1 into the corner109C to push sludge against the walls (FIG. 4A) and over the firstsludge mover blade (see arrow SO, FIG. 4A) away from the walls. Thepulled first tensile structure 126-3 is shown in FIG. 4B pulling tightlyaround the pulleys and on the second tensile structure 122-3 to furthertighten the slack, which further tightening is shown by structure 122-3being taut between the pulleys 135-2-1 and 135-2-2.

The method moves to operation 334 of pulling on the second tensilestructure to move the second sludge mover blade toward the first sludgemover blade, the pulled second tensile structure pulling around thepulleys and on the first tensile structure to move the first sludgemover blade toward the second sludge mover blade, the moving bladespushing sludge over the second sludge mover blade away from the walls.The pulling may be on the second tensile structure 122-3 to move thesecond sludge mover blade 110-2 in direction 114C toward the firstsludge mover blade 110-1. The pulled second tensile structure 122-3pulls around the pulleys (FIG. 2C) to cause the structure 122-3 to flex.The pulled and flexed structure 122-3 pulls around the pulleys and onthe first tensile structure 126-3. The structure 126-3 was at locationZ1 (FIG. 4C), and by the pull of structure 122-3 acting around thepulleys structure 126-3 is moved in direction 104C and moves the firstsludge mover blade 110-1 from location Z1 toward the blade stop locationZBS and toward the second sludge mover blade 110-2. These are theoppositely-moving blades 110-1 and 110-2 pushing sludge 102SO over thesecond sludge mover blade 110-2 away from the walls.

The method moves to operation 336 of pulling on the first tensilestructure toward the walls, the pulled first tensile structure pullingaround the pulleys and on the second tensile structure to move thesecond tensile structure and the second sludge mover blade to push thesludge out of the corner. The pulling may again be on the first tensilestructure 126-3, and is toward the walls 109L and 109E. The pulled firsttensile structure 126-3 pulls around the pulleys and pulls on the secondtensile structure 122-3. The structure 122-3 was flexed (FIG. 4C). Thepull by the structure 126-3 removes the flex, and moves the secondtensile structure 122-3 and the blade 110-2 into the taut configurationshown in FIG. 4B. As the second sludge mover blade 110-2 on the secondtensile structure 122-3 both become taut, the blade 110-2 pushes thesludge 102SO to the perimeter P, which is adjacent to the location Z2(FIG. 2C). The method is done.

By the above description, it is seen that embodiments of the presentinvention meet all of the above needs by providing sludge movingapparatus and methods. The present embodiments move adjacent blades 110at the same time but in opposite directions. In this manner, theseembodiments overcome the prior tendency for undesired movement of sludgein the return direction 114 due to all scrapers moving together at thesame time in the return direction. The present embodiments also providethin tensile members, e.g., 122-1, which further overcome the priortendency caused by the one net 32 (FIG. 1A) attached to and moving withall of the prior scrapers at the same time. Also, by providing the thintensile members, e.g., 120, 124, 128, and 138, commercial embodiments ofthe present invention do not require the prior reinforced net 32 drivenby the structural drive member that has high resistance to both tensionand compressive forces exerted parallel to the directions 34 and 36.Rather, there are pull-only structures, e.g., 128-1, 130-2, and 122-1,having high resistance to only tension force and virtually no resistanceto compressive forces. Without such extra structural member, there maybe reductions in the cost and weight of the present commercialembodiments, and reduction of energy required to move the blades 110through the sludge 102.

It is also seen that embodiments of the present invention meet all ofthe above needs by using the same speed of movement in the desireddirection 104 (and 104C) and in the return direction 114 (and 114C),which avoids the disadvantages of the prior higher speed for the returnstroke than for the forward stroke (e.g., 12 m/minute return vs., 3m/minute forward). The present same speeds avoid the prior agitation ofthe sludge particles, avoiding a cause of reintroducing settledparticles into the liquid that was clarified by the settler, andincreasing efficiency of the overall operations.

It is also seen that embodiments of the present invention meet all ofthe above needs by not having all blades 110 push the sludge in thedirection 104 in the same time period TP. Thus, all of the blades 110 donot push the sludge with the pusher surface PS at the same time. Thepresent embodiments avoid this by only pushing one-half of the pushersurfaces blades 110 through the sludge at the same time in the “to”direction 104. Thus, the total resistance by the sludge on the bladesmay reduce by one-half the power previously required to push all of thepusher surfaces (e.g., 46) of the scrapers through the sludge at thesame time.

It is also seen that embodiments of the present invention meet all ofthe above needs by enabling use of a lower-power motor 131, as comparedto that required to push all of the pusher surfaces 46 of the scrapersthrough the sludge at the same time in the to direction. The motor 131requires less power for the present sludge pushing and due to thedecreased weight without the prior extra compressive member.

It is also seen that embodiments of the present invention meet all ofthe above needs by providing the tensile structures that are morecompliant with respect to uneven floors of the basin, which in turnresults in lower costs to initially provide a smoother floor for thebasin (e.g., of concrete) and lower repair costs in fixing the floor ofthe basin during repair.

It is also seen that embodiments of the present invention meet all ofthe above needs by providing alternatives to the priorgenerally-triangular cross-section scrapers, which require additionalcost to manufacture the convex and concave shapes of the scrapers 40.

It is also seen that embodiments of the present invention avoid theneed, in actual commercial practice, for the use of any structural drivemember other than the separate rails 122 and 126 that carry therespective blades themselves. This is by applying only tension, or pull,forces to each of the separate rails, and by connecting one rail motorsystem 140 to each of the separate rail assemblies (120 and 124) so thata pull force applied to one yoke 130-2 and rails 122-1 and 122-2 in one(e.g., forward, or “to”) direction is applied by those rails (via theyoke 130-1) to the other rails 126-1 and 126-2 in the opposite (e.g.,return, or “fro”) direction. In this manner, each rail 122 and 126 maybe fabricated from material having minimum, or reduced, structuralcharacteristics. Such material need have a characteristic of highresistance only to tension forces, and need have low (or no) resistanceto compressive forces. This characteristic greatly reduces the cost ofthe sludge collection system, yet each rail 122 and 126 is structurallysufficient to carry and drive the blades 110 through the sludge 102 asthe respective rail 122 or 126 moves across the bottom 106 of the basin.As a result of the new combination of the low-cost blades 110 with thesignificantly improved configuration of the drive 116, during therespective “to” and “fro” movements the blades 110 resist those tensionforces and the drive 116 does not apply compressive forces to the rails.Thus, the present invention eliminates the above-described prior extrastructural drive member that has high resistance to both tension andcompressive forces.

Although the foregoing has been described in some detail for purposes ofclarity or understanding, it will be appreciated that certain changesand modifications may be practiced within the scope of the appendedclaims. Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalents of the appended claims.

1. Apparatus for moving material relative to a floor of a basin,comprising: at least one first blade having a first orientation; atleast one second blade having the same orientation as the at least onefirst blade; at least one third blade having a second orientation; atleast one fourth blade having the same orientation as the at least onethird blade; the at least one first and second blades are located on asingle axis; the at least one third blade and at least one fourth bladeare located on the same axis as and apart from the at least one firstand second blades; a reciprocating drive configured to simultaneouslymove each of the at least one first, second, third and fourth bladesrelative to the floor of the basin; and wherein the at least one firstand second blades have a first orientation to move material relative toa floor of a basin in a first direction, wherein the at least one thirdand fourth blades have a second orientation to move material relative toa floor of a basin in a second direction, and wherein the firstdirection is different from the second direction.
 2. An apparatus asrecited in claim 1, wherein: the drive comprises a first support for theat least one first blade and the at least one third blade, and a secondsupport for the at least one second blade and the at least one fourthblade, the first support and the second supports being separate fromeach other.
 3. An apparatus as recited in claim 2, wherein: the drive isfurther configured with at least one direction-reversal unit connectedbetween the first and second supports.
 4. An apparatus as recited inclaim 3, wherein: the drive is further configured with a first pull-onlydriver connected to the first support and with a second pull-only driverconnected to the second support.
 5. An apparatus as recited in claim 4,wherein: the drive is configured to simultaneously move each of the atleast one first, second, third and fourth blades relative to the floorof the basin by actuating one of the pull-only drivers to move one ofthe first or second supports in the first or the second direction sothat the at least one direction reversing unit causes the drive to movethe other of the first or second support in the other direction tosimultaneously move the respective blades and the material in the firstand second directions.
 6. An apparatus as recited in claim 4, wherein:the first support is comprised of a first tensile member fortransferring tensile forces and wherein the first pull-only driverapplies tensile forces to the first tensile member; and the secondsupport is comprised of a second tensile member for transferring tensileforces and the second pull-only driver applies tensile forces to thesecond tensile member.
 7. An apparatus as recited in claim 6, wherein:each of the first and second supports is configured with a first end anda second end; the at least one direction-reversal unit is configuredwith at least one pulley, the at least one pulley comprising a firstpulley; the at least one direction-reversal unit further comprising athird tensile member connected to the first end of the first support andextending around the first pulley and connected to the first end of thesecond support; and the first pull-only driver is connected to thesecond end of the first support and the second pull-only driver isconnected to the second end of the second support.
 8. An apparatus asrecited in claim 1, wherein the drive configuration providing thesimultaneous movement of each of the at least one first and third bladein opposition to the at least one second and fourth blade comprisesalternatively moving each blade toward and away from the other blade. 9.An apparatus as recited in claim 8, wherein: the drive is furtherconfigured so that the alternatively moving each blade is between firstlocation and second locations and so that there are blade stop locationsbetween the first and second locations, the second locations beingdesired locations to which the material is to be moved from locationsbetween the first locations and the second locations.
 10. An apparatusas recited in claim 9, wherein the at least one first, second, third andfourth blades are further configured so that as the at least one firstand at least one third blade are moved from the first location to theblade stop locations and as the at least one second blade and at leastone fourth blade are moved from the second locations to the blade stoplocations, spillover material is pushed by the at least one first bladeand at least one third blade over the at least one second blade and atleast one fourth blade respectively.
 11. An apparatus as recited inclaim 10, wherein: the drive is further configured so that after thespillover the at least one second blade and the at least one fourthblade are moved from the blade stop location to the second location; andthe at least one second blade and the at least one fourth blade areconfigured so that as the at least one second blade and the at least onefourth blade are moved from the blade stop locations to the secondlocations the spillover material is pushed by the at least one secondblade and the at least one fourth blade to the second locations.
 12. Anapparatus as recited in claim 1, wherein the drive provides simultaneousmovement of the at least one first and third blades in opposition to theat least one second and fourth blade such that the movement of each ofthe at least one first and third blades away from the at least onesecond and fourth blades respectively occurs near simultaneously.
 13. Anapparatus as recited in claim 12, wherein: the drive is furtherconfigured so that the simultaneous movement is between a first locationand a second locations and so that there are blade stop locationsbetween the first and second locations, the second locations beingdesired locations to which the material is to be moved from locationsbetween the first locations and the second locations.
 14. An apparatusas recited in claim 13, wherein: the basin is configured with a firstwall intersecting the floor; and when the at least one first blade andthe at least one third blade are moved from the blade stop locations tothe first locations the at least one first blade and the at least onethird blade causes material to move against the first wall and spillover the at least one first blade and the at least one third blade andtoward the blade stop locations.
 15. Apparatus for moving sludge in afirst and a second direction relative to a floor of a basin, comprising:at least one first blade extending at least partly across the basin; atleast one second blade on the same axis as the at least one first blade,spaced from the at least one first blade and extending in spacedopposition to the at least one first blade; at least one third bladeextending at least partly across the basin; at least one fourth blade onthe same axis as the at least one third blade, spaced apart from the atleast one third blade and extending in spaced opposition to the at leastone third blade; a drive configured to simultaneously move each of thespaced at least one first and second blades along a common planerelative to the floor of the basin in opposition to each other, thesimultaneous movement comprising the drive moving the at least one firstblade in the first direction and the drive simultaneously moving the atleast one second blade in a second direction opposite to the firstdirection; the drive further configured to simultaneously move each ofthe spaced at least one third and fourth blades along a common planerelative to the floor of the basin in opposition to each other, thesimultaneous movement comprising the drive moving the at least one thirdblade in the first direction and the drive simultaneously moving the atleast one fourth blade in a second direction opposite to the firstdirection; wherein the simultaneous moving of the at least one first andsecond blades causes sludge to move in the first direction, wherein thesimultaneous moving of the at least one third and fourth blades causessludge to move in the second direction, and wherein the sludge moved ina first direction and the sludge moved in a second direction is moved toa sludge outlet located between the location of the at least one firstand second blades and the location of the at least one third and fourthblades.
 16. Apparatus as recited in claim 15, wherein: each of thefirst, second, third and fourth blades are configured with a crosssection comprising a pusher surface and a receiver surface tilted awayfrom the pusher surface; the simultaneous movement of each of the spacedat least one first and second blades along the common plane and in theopposite directions causes transfer of the sludge by the at least onefirst blade pushing the sludge in the first direction along the receiversurface of the at least one second blade that is moving in the seconddirection so that the pushed sludge spills in the first direction pastthe at least one second blade to provide spillover sludge adjacent tothe pusher surface of the at least one second blade, the simultaneousmovement of each of the spaced at least one third and fourth bladesalong the common plane and in the opposite directions causes transfer ofthe sludge by the at least one fourth blade pushing the sludge in thefirst direction along the receiver surface of the at least one thirdblade that is moving in the second direction so that the pushed sludgespills in the first direction past the at least one third blade toprovide spillover sludge adjacent to the pusher surface of the at leastone third blade.
 17. Apparatus as recited in claim 16, furthercomprising: first and second tensile members separately supporting therespective at least one first and third blades and respective at leastone second and fourth blades for separate movement, each of the tensilemembers having a given tensile strength value sufficient to enable therespective tensile member to respond to a pull of the drive to cause therespective pusher surface of the respective blade to push sludge overthe oppositely moving blade, and each of the tensile members having acompression strength of a value substantially less than that of thegiven tensile strength value.
 18. Apparatus as recited in claim 17,further comprising: a direction-reversal mechanism configured betweenthe first and second tensile members; wherein a pull of the drive on thefirst tensile member in the first direction causes the first tensilemember to actuate the direction-reversal mechanism and apply a pull onthe second tensile member in the second direction to move the secondtensile member and the at least one second blade and the at least onefourth blade in the second direction during movement of the firsttensile member and the at least one first blade and the at least onethird blade in the first direction.
 19. Apparatus as recited in claim15, wherein: the drive is further configured with a first tensileassembly connecting the first and third blades and a second tensileassembly connecting the second and fourth blades; the drive is furtherconfigured with a direction-reversal mechanism between the first andsecond tensile assemblies; the drive is further configured to pull thefirst tensile assembly and the first and third blades in the firstdirection and then to pull the second tensile assembly and the secondand fourth blades in the first direction; the pulled first tensileassembly is configured to actuate the direction-reversal mechanism tosimultaneously pull the second tensile assembly and each of the secondand fourth blades in the common plane in the second direction; and thepulled second tensile assembly is configured to actuate thedirection-reversal mechanism to simultaneously pull the first tensileassembly and each of the first and third blades in the common plane inthe second direction.
 20. Apparatus as recited in claim 19, wherein: thefirst and third blades moving in the first direction move in oppositionto the respective second and fourth blades moving in the seconddirection to transfer sludge past the respective second and fourthblades in the first direction, and the second blade moving in the firstdirection moves in opposition to the third blade moving in the seconddirection to transfer the sludge past the third blade in the firstdirection.
 21. Apparatus as recited in claim 15, wherein: the drive isfurther configured with a first tensile assembly connecting the firstand third blades and with a second tensile assembly connecting thesecond and fourth blades; the apparatus further comprises a set offifth, sixth, seventh, and eighth blades for moving sludge in the seconddirection relative to the floor of the basin during movement of thesludge by the first, second, third and fourth blades in the firstdirection relative to the floor of the basin, the set of bladescomprising: the fifth blade configured to extend at least partly acrossthe basin and connected to the first tensile assembly to movesimultaneously with and in the same direction as the first and thirdblades; the sixth blade configured to extend at least partly across thebasin and connected to the second tensile assembly to movesimultaneously with and in the same direction as the second and fourthblades; the seventh blade configured to extend at least partly acrossthe basin and connected to the second assembly to move simultaneouslywith and in the same direction as the first, third and fifth blades; theeighth blade configured to extend at least partly across the basin andconnected to the second tensile assembly to move simultaneously with andin the same direction as the second, fourth, and sixth blades; thefifth, sixth, seventh, and eighth blades being arranged in a spacedsequence comprising the fifth blade followed by the sixth blade followedby the seventh blade followed by the eighth blade; the first, second,third and fourth blades being oriented relative to the respective firstand second tensile assemblies to move the sludge in the first directionrelative to the floor of the basin; and the fifth, sixth, seventh, andeighth blades being oriented oppositely to the orientation of the first,second, third and fourth blades to move the sludge in the seconddirection relative to the floor of the basin simultaneously with theother movement of the sludge in the first direction.
 22. Apparatus formoving sludge relative to a floor of a basin, comprising: a plurality ofblades configured about a common axis to extend at least partly acrossthe basin in an adjacent arrangement; a first tensile member for movingat least a first and a third one of the plurality of blades adjacent tothe floor; a second tensile member for moving at least a second and afourth one of the plurality of blades adjacent to the floor; the atleast one first blade and the at least one second blade adjacent to oneanother about a common axis; the at least one third blade and the atleast one fourth blade adjacent to one another about a common axis;wherein the at least one first and second blades have a firstorientation to move material relative to the floor of the basin in afirst direction, wherein the at least one third and fourth blades have asecond orientation to move material on the floor of the basin in asecond direction, and wherein the first direction is different from thesecond direction; a drive configured to move the first and secondtensile members and the respective at least one first, second, third andfourth blades along the plane relative to the floor, the movementcomprising the at least one first blade moving in a first directionrelative to the floor and in opposition to the at least one second bladeand comprising the at least one second blade moving in a seconddirection opposite to the first direction and in opposition to the atleast one first blade and at least one fourth blade moving in a seconddirection relative to the floor and in opposition to the at least onethird blade and comprising the at least one third blade moving in afirst direction opposite to the second direction and in opposition tothe at least one fourth blade such that the drive pulling the firsttensile member in one direction causes the second tensile member to movein the opposite direction; and a direction-reversal mechanism betweenthe first and second tensile members, the direction-reversal mechanismbeing actuated by the first tensile member moving in the first directionto move the second tensile member in the second direction, thedirection-reversal mechanism being actuated by the second tensile membermoving in the first direction to move the first tensile member in thesecond direction.
 23. Apparatus as recited in claim 22, wherein thedirection-reversal mechanism is configured so that each time the firsttensile member moves in the second direction and the second tensilemember moves in the first direction pairs of the blades move apart fromeach other, the pairs comprising one blade carried by the first tensilemember and one blade carried by the second tensile member.
 24. Apparatusas recited in claim 22, wherein the direction-reversal mechanism isconfigured so that each time the first tensile member moves in thesecond direction and the second tensile member moves in the firstdirection pairs of the blades move toward each other, the pairscomprising one blade carried by the first tensile member and one bladecarried by the second tensile member.